An ear-worn electronic device comprises a housing configured to fit at least partially in an ear of a wearer, a power source situated in the housing, and a temperature sensor arrangement situated in or on the housing and coupled to the power source. The temperature sensor arrangement is configured to generate sensor signals in response to heat generated in the wearer's ear and a controller, situated in the housing and coupled to the power source and the temperature sensor arrangement, is configured to assess a fit of the device using the sensor signals.