diff --git a/esphome/components/i2c/__init__.py b/esphome/components/i2c/__init__.py
index 3884204ae5..88a497ddf2 100644
--- a/esphome/components/i2c/__init__.py
+++ b/esphome/components/i2c/__init__.py
@@ -94,7 +94,13 @@ def _bus_declare_type(value):
 
 
 def _rp2040_i2c_controller(pin):
-    """Return the I2C controller number (0 or 1) for a given RP2040/RP2350 GPIO pin."""
+    """Return the I2C controller number (0 or 1) for a given RP2040/RP2350 GPIO pin.
+
+    See RP2040 datasheet Table 2 (section 1.4.3, "GPIO Functions"):
+    https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf
+    See RP2350 datasheet Table 7 (section 9.4, "Function Select"):
+    https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf
+    """
     return (pin // 2) % 2
 
 
diff --git a/esphome/components/i2c/i2c_bus_arduino.cpp b/esphome/components/i2c/i2c_bus_arduino.cpp
index e339fe59fc..3a511edfdb 100644
--- a/esphome/components/i2c/i2c_bus_arduino.cpp
+++ b/esphome/components/i2c/i2c_bus_arduino.cpp
@@ -22,7 +22,8 @@ void ArduinoI2CBus::setup() {
 #elif defined(USE_RP2040)
   // Select Wire instance based on pin assignment, not definition order.
   // RP2040 I2C controller is determined by GPIO: (pin / 2) % 2
-  // I2C0 SDA: GPIO 0,4,8,12,16,20,24,28  I2C1 SDA: GPIO 2,6,10,14,18,22,26
+  // See RP2040 datasheet Table 2 (section 1.4.3): https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf
+  // See RP2350 datasheet Table 7 (section 9.4): https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf
   if ((this->sda_pin_ / 2) % 2 == 0) {
     wire_ = &Wire;
   } else {