Abstract: The effect of improved heat tolerance through drought preconditioning on responses to drought preconditioning under heat stress was studied in two Kentucky bluegrasses. Plants of Kentucky bluegrass (Poa pratensis) cultivars “Midnight” (drought resistant) and “Brilliant” (drought sensitive) were well watered (non-preconditioned control) or exposed to two cycles of drought stress without irrigation (drought preconditioning) and then exposed to heat stress (35℃/30℃, day/night) for 25 days in growth chambers. Turf quality and other physiological parameters in leaves were determined at 0 (end of drought preconditioning and beginning of heat treatment), 5, 10, 15, 20, and 25 days of heat treatment. During the period of heat stress, drought-preconditioning of cv. “Brilliant” resulted in significantly (P＜0.05) higher turf quality compared with the non-preconditioned “Brilliant”. After 5 days of heat stress, osmotic potential gradually declined in drought-preconditioned “Brilliant”, but there was little change in the non-preconditionied “Brilliant”. Plants of drought-preconditioned “Brilliant” maintained significantly (P＜0.05) higher relative water content than those of non-preconditioned plants at 10 and 15 days of heat stress. The activities of superoxide dismutase and catalase were significantly (P＜0.05) higher in drought-preconditioned “Brilliant” than in non-preconditioned “Brilliant” at 10 and 20 days of heat stress, but electrolyte leakage was the reverse. There was significantly (P＜0.05) higher fatty acid (16∶0 and 18∶0) content in drought-preconditioned “Brilliant” than in non-preconditioned “Brilliant” after 15 days of heat stress, although the content of 18∶3 was the opposite. Drought-preconditioned “Midnight” had a higher double bond index (DBI) than non-preconditioned “Brilliant”. The physiological parameters were not significantly different in the two treatments in “Midnight” under heat stress. In conclusion, drought preconditioning improved heat tolerance in the drought sensitive cv. “Brilliant” but failed to improve heat tolerance in the drought resistant cv. “Midnight'. Improved heat tolerance through drought preconditioning in “Brilliant” was associated with increased osmoregulatory ability and the promotion of antioxidant activities which can protect unsaturated fatty acids from damage. These changes may play an important role in improving leaf relative water content, protecting membrane systems and delaying leaf senescence.