diff --git a/tests/component_tests/font/.gitattributes b/tests/component_tests/font/.gitattributes
new file mode 100644
index 00000000000..4df6726184f
--- /dev/null
+++ b/tests/component_tests/font/.gitattributes
@@ -0,0 +1,2 @@
+*.pcf -text
+*.ttf -text
diff --git a/tests/component_tests/font/NotoSans-Regular.ttf b/tests/component_tests/font/NotoSans-Regular.ttf
new file mode 100644
index 00000000000..a1b8994edea
Binary files /dev/null and b/tests/component_tests/font/NotoSans-Regular.ttf differ
diff --git a/tests/component_tests/font/__init__.py b/tests/component_tests/font/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/component_tests/font/test_font.py b/tests/component_tests/font/test_font.py
new file mode 100644
index 00000000000..55e27ae84ce
--- /dev/null
+++ b/tests/component_tests/font/test_font.py
@@ -0,0 +1,337 @@
+"""Tests for the font component.
+
+Focuses on verifying that long multi-byte (Chinese/CJK) glyph strings
+are correctly processed through the font configuration pipeline.
+"""
+
+import functools
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from esphome.components.font import (
+    CONF_BPP,
+    CONF_EXTRAS,
+    CONF_GLYPHSETS,
+    CONF_IGNORE_MISSING_GLYPHS,
+    CONF_RAW_GLYPH_ID,
+    FONT_CACHE,
+    flatten,
+    glyph_comparator,
+    to_code,
+    validate_font_config,
+)
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_FILE,
+    CONF_GLYPHS,
+    CONF_ID,
+    CONF_PATH,
+    CONF_RAW_DATA_ID,
+    CONF_SIZE,
+    CONF_TYPE,
+)
+
+FONT_DIR = Path(__file__).parent
+FONT_PATH = FONT_DIR / "NotoSans-Regular.ttf"
+
+# 200 unique CJK Unified Ideograph characters (U+4E00..U+4EC7)
+CHINESE_200 = "".join(chr(cp) for cp in range(0x4E00, 0x4EC8))
+
+
+def _file_conf() -> dict:
+    return {CONF_PATH: str(FONT_PATH), CONF_TYPE: "local"}
+
+
+def _make_config(
+    glyphs: list[str],
+    *,
+    ignore_missing: bool = False,
+    size: int = 20,
+    bpp: int = 1,
+    extras: list | None = None,
+    glyphsets: list | None = None,
+) -> dict:
+    """Build a config dict matching what FONT_SCHEMA produces."""
+    return {
+        CONF_FILE: _file_conf(),
+        CONF_GLYPHS: glyphs,
+        CONF_GLYPHSETS: glyphsets or [],
+        CONF_IGNORE_MISSING_GLYPHS: ignore_missing,
+        CONF_SIZE: size,
+        CONF_BPP: bpp,
+        CONF_EXTRAS: extras or [],
+    }
+
+
+@pytest.fixture(autouse=True)
+def _load_font():
+    """Load the test font into FONT_CACHE and clean up afterwards."""
+    fc = _file_conf()
+    FONT_CACHE[fc] = FONT_PATH
+    yield
+    FONT_CACHE.store.clear()
+
+
+# ---------- flatten / glyph_comparator helpers ----------
+
+
+def test_flatten_splits_chinese_string_into_chars():
+    """A single string of 200 Chinese characters must become 200 individual chars."""
+    result = flatten([CHINESE_200])
+    assert len(result) == 200
+    assert all(len(c) == 1 for c in result)
+    assert result[0] == "\u4e00"
+    assert result[-1] == "\u4ec7"
+
+
+def test_flatten_multiple_chinese_strings():
+    """Multiple glyph strings are concatenated then split correctly."""
+    s1 = CHINESE_200[:100]
+    s2 = CHINESE_200[100:]
+    result = flatten([list(s1), list(s2)])
+    assert len(result) == 200
+
+
+def test_glyph_comparator_orders_chinese_by_utf8():
+    """glyph_comparator must order CJK characters by their UTF-8 byte sequence."""
+    chars = list(CHINESE_200[:10])
+    sorted_chars = sorted(chars, key=functools.cmp_to_key(glyph_comparator))
+    # CJK block is contiguous and UTF-8 order matches codepoint order here
+    assert sorted_chars == chars
+
+
+def test_glyph_comparator_mixed_ascii_and_chinese():
+    """ASCII characters sort before CJK characters (lower UTF-8 bytes)."""
+    assert glyph_comparator("A", "\u4e00") == -1
+    assert glyph_comparator("\u4e00", "A") == 1
+    assert glyph_comparator("\u4e00", "\u4e00") == 0
+
+
+# ---------- validate_font_config ----------
+
+
+def test_long_chinese_glyphs_raises_missing_error():
+    """200 Chinese chars not present in NotoSans must raise Invalid with the correct count."""
+    config = _make_config([CHINESE_200])
+    with pytest.raises(cv.Invalid, match=r"missing 200 glyphs"):
+        validate_font_config(config)
+
+
+def test_long_chinese_glyphs_error_mentions_overflow():
+    """When more than 10 glyphs are missing the error should mention the remainder."""
+    config = _make_config([CHINESE_200])
+    with pytest.raises(cv.Invalid, match=r"and 190 more"):
+        validate_font_config(config)
+
+
+def test_duplicate_chinese_glyphs_detected():
+    """Duplicate CJK characters within a single glyph string must be caught."""
+    duped = "\u4e00\u4e01\u4e00"  # first char repeated
+    config = _make_config([duped])
+    with pytest.raises(cv.Invalid, match="duplicate"):
+        validate_font_config(config)
+
+
+def test_duplicate_chinese_across_strings():
+    """Duplicates across separate glyph strings are also caught."""
+    config = _make_config(["\u4e00\u4e01", "\u4e01\u4e02"])
+    with pytest.raises(cv.Invalid, match="duplicate"):
+        validate_font_config(config)
+
+
+def test_no_false_duplicates_in_200_unique_chinese():
+    """200 unique CJK characters must not trigger the duplicate check."""
+    config = _make_config([CHINESE_200])
+    # Should not raise duplicate error — it should reach the missing-glyph check instead
+    with pytest.raises(cv.Invalid, match="missing"):
+        validate_font_config(config)
+
+
+def test_valid_latin_glyphs_pass_validation():
+    """Latin characters present in NotoSans-Regular pass validation without error."""
+    config = _make_config(["ABCabc123"])
+    result = validate_font_config(config)
+    assert result is not None
+    assert result[CONF_SIZE] == 20
+
+
+def test_long_latin_glyphs_pass_validation():
+    """A long string of supported Latin glyphs passes validation."""
+    # 95 printable ASCII characters that NotoSans supports
+    latin = "".join(chr(cp) for cp in range(0x21, 0x7F))
+    config = _make_config([latin])
+    result = validate_font_config(config)
+    assert result is not None
+
+
+def test_mixed_latin_and_chinese_glyphs_error():
+    """Mixing valid Latin and invalid Chinese chars reports missing Chinese glyphs."""
+    chinese_10 = CHINESE_200[:10]
+    config = _make_config(["ABC", chinese_10])
+    with pytest.raises(cv.Invalid, match=r"missing 10 glyphs"):
+        validate_font_config(config)
+
+
+def test_single_chinese_char_glyph():
+    """A single Chinese character is correctly handled as one glyph."""
+    config = _make_config(["\u4e00"])
+    with pytest.raises(cv.Invalid, match=r"missing 1 glyph[^s]"):
+        validate_font_config(config)
+
+
+def test_chinese_glyphs_as_individual_list_items():
+    """Chinese chars provided as separate list items are handled the same as a single string."""
+    chars_as_list = list(CHINESE_200[:50])
+    config = _make_config(chars_as_list)
+    with pytest.raises(cv.Invalid, match=r"missing 50 glyphs"):
+        validate_font_config(config)
+
+
+# ---------- YAML parsing ----------
+
+
+def test_yaml_long_latin_glyphs_parsed_and_validated(tmp_path):
+    """200 Latin Extended chars on a single YAML line are parsed intact and pass validation."""
+    from esphome.yaml_util import load_yaml
+
+    latin_long = "".join(chr(cp) for cp in range(0x100, 0x1C8))
+    yaml_file = tmp_path / "font_test.yaml"
+    yaml_file.write_text(
+        f'font:\n  - file: "NotoSans-Regular.ttf"\n    glyphs: "{latin_long}"\n',
+        encoding="utf-8",
+    )
+
+    parsed = load_yaml(yaml_file)
+    raw_glyphs = parsed["font"][0]["glyphs"]
+
+    # YAML must preserve every Unicode character on the single line
+    assert raw_glyphs == latin_long
+    assert len(raw_glyphs) == 200
+
+    # Feed through validate_font_config to confirm all glyphs are accepted
+    config = _make_config([raw_glyphs])
+    result = validate_font_config(config)
+    assert result is not None
+
+
+@pytest.mark.parametrize(
+    "glyphs_str",
+    [
+        " ABC",  # space at start
+        "AB CD",  # space in middle
+        "ABC ",  # space at end
+    ],
+    ids=["start", "middle", "end"],
+)
+def test_yaml_space_in_glyphs_preserved(tmp_path, glyphs_str):
+    """A space character in a glyphs string must survive YAML round-trip and validation."""
+    from esphome.yaml_util import load_yaml
+
+    yaml_file = tmp_path / "font_test.yaml"
+    yaml_file.write_text(
+        f'font:\n  - file: "NotoSans-Regular.ttf"\n    glyphs: "{glyphs_str}"\n',
+        encoding="utf-8",
+    )
+
+    parsed = load_yaml(yaml_file)
+    raw_glyphs = parsed["font"][0]["glyphs"]
+
+    assert raw_glyphs == glyphs_str
+    assert " " in raw_glyphs
+
+    # Space and ASCII letters are all in NotoSans — validation must pass
+    config = _make_config([raw_glyphs])
+    result = validate_font_config(config)
+    assert result is not None
+
+
+# ---------- to_code generation ----------
+
+
+# 200 unique Latin Extended characters (U+0100..U+01C7), all present in NotoSans
+LATIN_LONG = "".join(chr(cp) for cp in range(0x100, 0x1C8))
+
+
+@pytest.fixture
+def mock_cg():
+    """Mock all cg codegen functions used by to_code."""
+    with (
+        patch("esphome.components.font.cg.add_define") as mock_define,
+        patch("esphome.components.font.cg.progmem_array") as mock_progmem,
+        patch("esphome.components.font.cg.static_const_array") as mock_static,
+        patch("esphome.components.font.cg.new_Pvariable") as mock_new_pvar,
+    ):
+        mock_progmem.return_value = MagicMock()
+        mock_static.return_value = MagicMock()
+        yield {
+            "add_define": mock_define,
+            "progmem_array": mock_progmem,
+            "static_const_array": mock_static,
+            "new_Pvariable": mock_new_pvar,
+        }
+
+
+@pytest.mark.asyncio
+async def test_to_code_long_latin_generates_all_glyphs(mock_cg):
+    """to_code must generate glyph data for every character in a long Latin string."""
+    glyph_count = len(LATIN_LONG)  # 200
+    config = _make_config([LATIN_LONG])
+    config[CONF_ID] = MagicMock()
+    config[CONF_RAW_DATA_ID] = MagicMock()
+    config[CONF_RAW_GLYPH_ID] = MagicMock()
+
+    await to_code(config)
+
+    # USE_FONT define must be emitted
+    mock_cg["add_define"].assert_any_call("USE_FONT")
+
+    # progmem_array receives the combined bitmap data (non-empty)
+    mock_cg["progmem_array"].assert_called_once()
+    bitmap_data = mock_cg["progmem_array"].call_args.args[1]
+    assert len(bitmap_data) > 0
+
+    # static_const_array receives one entry per unique glyph
+    mock_cg["static_const_array"].assert_called_once()
+    glyph_initializer = mock_cg["static_const_array"].call_args.args[1]
+    assert len(glyph_initializer) == glyph_count
+
+    # new_Pvariable is called with the correct glyph count
+    mock_cg["new_Pvariable"].assert_called_once()
+    pvar_args = mock_cg["new_Pvariable"].call_args.args
+    assert pvar_args[2] == glyph_count  # len(glyph_initializer)
+    assert pvar_args[8] == 1  # bpp
+
+
+@pytest.mark.asyncio
+async def test_to_code_glyph_entries_contain_expected_fields(mock_cg):
+    """Each glyph initializer entry must have 7 fields: codepoint, data ptr, advance, offset_x, offset_y, w, h."""
+    config = _make_config([LATIN_LONG])
+    config[CONF_ID] = MagicMock()
+    config[CONF_RAW_DATA_ID] = MagicMock()
+    config[CONF_RAW_GLYPH_ID] = MagicMock()
+
+    await to_code(config)
+
+    glyph_initializer = mock_cg["static_const_array"].call_args.args[1]
+    for entry in glyph_initializer:
+        assert len(entry) == 7, f"Glyph entry should have 7 fields, got {len(entry)}"
+        codepoint = entry[0]
+        assert isinstance(codepoint, int)
+        assert 0x100 <= codepoint <= 0x1C7
+
+
+@pytest.mark.asyncio
+async def test_to_code_glyphs_sorted_by_utf8(mock_cg):
+    """Glyphs in the initializer must be sorted by UTF-8 byte order."""
+    config = _make_config([LATIN_LONG])
+    config[CONF_ID] = MagicMock()
+    config[CONF_RAW_DATA_ID] = MagicMock()
+    config[CONF_RAW_GLYPH_ID] = MagicMock()
+
+    await to_code(config)
+
+    glyph_initializer = mock_cg["static_const_array"].call_args.args[1]
+    codepoints = [entry[0] for entry in glyph_initializer]
+    assert codepoints == sorted(codepoints)
diff --git a/tests/components/font/.gitattributes b/tests/components/font/.gitattributes
index 63ab00e9f28..4df6726184f 100644
--- a/tests/components/font/.gitattributes
+++ b/tests/components/font/.gitattributes
@@ -1 +1,2 @@
-*.pcf        -text
+*.pcf -text
+*.ttf -text