diff --git a/esphome/components/ct_clamp/ct_clamp_sensor.cpp b/esphome/components/ct_clamp/ct_clamp_sensor.cpp
index 51b0f1318c..d555befcde 100644
--- a/esphome/components/ct_clamp/ct_clamp_sensor.cpp
+++ b/esphome/components/ct_clamp/ct_clamp_sensor.cpp
@@ -33,7 +33,10 @@ void CTClampSensor::update() {
 
     const float rms_ac_dc_squared = this->sample_squared_sum_ / this->num_samples_;
     const float rms_dc = this->sample_sum_ / this->num_samples_;
-    const float rms_ac = std::sqrt(rms_ac_dc_squared - rms_dc * rms_dc);
+    const float rms_ac_squared = rms_ac_dc_squared - rms_dc * rms_dc;
+    float rms_ac = 0;
+    if (rms_ac_squared > 0)
+      rms_ac = std::sqrt(rms_ac_squared);
     ESP_LOGD(TAG, "'%s' - Raw AC Value: %.3fA after %d different samples (%d SPS)", this->name_.c_str(), rms_ac,
              this->num_samples_, 1000 * this->num_samples_ / this->sample_duration_);
     this->publish_state(rms_ac);