diff --git a/esphome/components/sm300d2/sm300d2.cpp b/esphome/components/sm300d2/sm300d2.cpp
index d542582fcb..e41a4855db 100644
--- a/esphome/components/sm300d2/sm300d2.cpp
+++ b/esphome/components/sm300d2/sm300d2.cpp
@@ -29,8 +29,11 @@ void SM300D2Sensor::update() {
   }
 
   uint16_t calculated_checksum = this->sm300d2_checksum_(response);
+  // Occasionally the checksum has a +/- 0x80 offset. Negative temperatures are
+  // responsible for some of these. The rest are unknown/undocumented.
   if ((calculated_checksum != response[SM300D2_RESPONSE_LENGTH - 1]) &&
-      (calculated_checksum - 0x80 != response[SM300D2_RESPONSE_LENGTH - 1])) {
+      (calculated_checksum - 0x80 != response[SM300D2_RESPONSE_LENGTH - 1]) &&
+      (calculated_checksum + 0x80 != response[SM300D2_RESPONSE_LENGTH - 1])) {
     ESP_LOGW(TAG, "SM300D2 Checksum doesn't match: 0x%02X!=0x%02X", response[SM300D2_RESPONSE_LENGTH - 1],
              calculated_checksum);
     this->status_set_warning();
@@ -46,7 +49,10 @@ void SM300D2Sensor::update() {
   const uint16_t tvoc = (response[6] * 256) + response[7];
   const uint16_t pm_2_5 = (response[8] * 256) + response[9];
   const uint16_t pm_10_0 = (response[10] * 256) + response[11];
-  const float temperature = response[12] + (response[13] * 0.1);
+  // A negative value is indicated by adding 0x80 (128) to the temperature value
+  const float temperature = ((response[12] + (response[13] * 0.1)) > 128)
+                                ? (((response[12] + (response[13] * 0.1)) - 128) * -1)
+                                : response[12] + (response[13] * 0.1);
   const float humidity = response[14] + (response[15] * 0.1);
 
   ESP_LOGD(TAG, "Received CO₂: %u ppm", co2);