The effect of thermal cycling exposure on room temperature flexural strength was examined in hot-pressed ZrB2-SiC composite undergone cyclic heating-cooling test at 1200 and 1400 degrees C in air for up to 1000 or 500 cycles. For the post-tested samples at 1200 degrees C, the flexural strength of the composite initially increased and subsequently degraded with increase of number of thermal cycles (N). The strength retention displayed by the composite after N=1000 cycles was approximately 80%. For the post-tested samples at 1400 degrees C, however, the flexural strength decreased with increase of N. After N=500 cycles, the strength retention was approximately 45%. The strength decrease was associated with the formation and coarsening of defects in the oxidized reactive layer and the delamination of the outermost thinner dense oxide layer.