Imaging systems may be provided with image sensors and verification circuitry. Verification circuitry may be configured to continuously verify proper operation of the image sensor during operation. Verification circuitry may include one or more heating elements formed on a common substrate with image pixels of the image sensor. Verification data may be generated by powering on the heating elements and collecting charges generated in image pixels of the image sensor in response to heat generated by the powered heating element. Heat image charges may be read out using the same readout circuitry that is used to readout imaging data generated in response to incoming light. Heat image data may be used to verify proper operation of all components of an imaging system. Based on a comparison of the verification data with a predetermined standard, an imaging system may continue to operate normally or corrective action may be taken.