diff --git a/esphome/components/debug/debug_rp2040.cpp b/esphome/components/debug/debug_rp2040.cpp
index c9d41942db..8dc84a2673 100644
--- a/esphome/components/debug/debug_rp2040.cpp
+++ b/esphome/components/debug/debug_rp2040.cpp
@@ -1,23 +1,81 @@
 #include "debug_component.h"
 #ifdef USE_RP2040
+#include "esphome/core/defines.h"
 #include "esphome/core/log.h"
 #include <Arduino.h>
+#include <hardware/watchdog.h>
+#if defined(PICO_RP2350)
+#include <hardware/structs/powman.h>
+#else
+#include <hardware/structs/vreg_and_chip_reset.h>
+#endif
+#ifdef USE_RP2040_CRASH_HANDLER
+#include "esphome/components/rp2040/crash_handler.h"
+#endif
 namespace esphome {
 namespace debug {
 
 static const char *const TAG = "debug";
 
-const char *DebugComponent::get_reset_reason_(std::span<char, RESET_REASON_BUFFER_SIZE> buffer) { return ""; }
+const char *DebugComponent::get_reset_reason_(std::span<char, RESET_REASON_BUFFER_SIZE> buffer) {
+  char *buf = buffer.data();
+  const size_t size = RESET_REASON_BUFFER_SIZE;
+  size_t pos = 0;
+
+#if defined(PICO_RP2350)
+  uint32_t chip_reset = powman_hw->chip_reset;
+  if (chip_reset & 0x04000000)  // HAD_GLITCH_DETECT
+    pos = buf_append_str(buf, size, pos, "Power supply glitch|");
+  if (chip_reset & 0x00040000)  // HAD_RUN_LOW
+    pos = buf_append_str(buf, size, pos, "RUN pin|");
+  if (chip_reset & 0x00020000)  // HAD_BOR
+    pos = buf_append_str(buf, size, pos, "Brown-out|");
+  if (chip_reset & 0x00010000)  // HAD_POR
+    pos = buf_append_str(buf, size, pos, "Power-on reset|");
+#else
+  uint32_t chip_reset = vreg_and_chip_reset_hw->chip_reset;
+  if (chip_reset & 0x00010000)  // HAD_RUN
+    pos = buf_append_str(buf, size, pos, "RUN pin|");
+  if (chip_reset & 0x00000100)  // HAD_POR
+    pos = buf_append_str(buf, size, pos, "Power-on reset|");
+#endif
+
+  if (watchdog_caused_reboot()) {
+    bool handled = false;
+#ifdef USE_RP2040_CRASH_HANDLER
+    if (rp2040::crash_handler_has_data()) {
+      pos = buf_append_str(buf, size, pos, "Crash (HardFault)|");
+      handled = true;
+    }
+#endif
+    if (!handled) {
+      if (watchdog_enable_caused_reboot()) {
+        pos = buf_append_str(buf, size, pos, "Watchdog timeout|");
+      } else {
+        pos = buf_append_str(buf, size, pos, "Software reset|");
+      }
+    }
+  }
+
+  // Remove trailing '|'
+  if (pos > 0 && buf[pos - 1] == '|') {
+    buf[pos - 1] = '\0';
+  } else if (pos == 0) {
+    return "Unknown";
+  }
+
+  return buf;
+}
 
 const char *DebugComponent::get_wakeup_cause_(std::span<char, RESET_REASON_BUFFER_SIZE> buffer) { return ""; }
 
-uint32_t DebugComponent::get_free_heap_() { return rp2040.getFreeHeap(); }
+uint32_t DebugComponent::get_free_heap_() { return ::rp2040.getFreeHeap(); }
 
 size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE> buffer, size_t pos) {
   constexpr size_t size = DEVICE_INFO_BUFFER_SIZE;
   char *buf = buffer.data();
 
-  uint32_t cpu_freq = rp2040.f_cpu();
+  uint32_t cpu_freq = ::rp2040.f_cpu();
   ESP_LOGD(TAG, "CPU Frequency: %" PRIu32, cpu_freq);
   pos = buf_append_printf(buf, size, pos, "|CPU Frequency: %" PRIu32, cpu_freq);
 
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 70ac1574f0..b2517e2d7a 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -942,6 +942,28 @@ __attribute__((format(printf, 4, 5))) inline size_t buf_append_printf(char *buf,
 }
 #endif
 
+/// Safely append a string to buffer without format parsing, returning new position (capped at size).
+/// More efficient than buf_append_printf for plain string literals.
+/// @param buf Output buffer
+/// @param size Total buffer size
+/// @param pos Current position in buffer
+/// @param str String to append (must not be null)
+/// @return New position after appending (capped at size on overflow)
+inline size_t buf_append_str(char *buf, size_t size, size_t pos, const char *str) {
+  if (pos >= size) {
+    return size;
+  }
+  size_t remaining = size - pos - 1;  // reserve space for null terminator
+  size_t len = strlen(str);
+  if (len > remaining) {
+    len = remaining;
+  }
+  memcpy(buf + pos, str, len);
+  pos += len;
+  buf[pos] = '\0';
+  return pos;
+}
+
 /// Concatenate a name with a separator and suffix using an efficient stack-based approach.
 /// This avoids multiple heap allocations during string construction.
 /// Maximum name length supported is 120 characters for friendly names.