Frequency‐modulation time‐delay spectrometry (FM‐TDS) has been implemented in photopyroelectric measurements of thermal diffusivity, on a series of well‐characterized samples. The strategy of FM‐TDS is sample excitation by a fast linear frequency sweep, whose autocorrelation function is mathematically equivalent to a Dirac delta function. The method permits the fast recovery of high‐quality frequency and impulse‐response information. Impulse responses recovered in the time‐delay domain showed good agreement with a Green’s function model of transient heat conduction. The present work demonstrates that the FM‐TDS measurement strategy yields photothermal information equivalent to that obtainable from a pulsed laser system, with much lower excitation power.