Aquaponics is a fast-growing subsector of aquaculture that combines recirculating aquaculture with hydroponic plant production. T he most common pairing of fish and plants in commercial systems currently is Nile tilapia and lettuce. Nile tilapia and lettuce have different thermal preferences for growing . Nile tilapia perform best in warm water around 30°C, while lettuce tends to grow best at cool temperatures around 20°C. Hence, the objective of this study was to evaluate the performance of four heat-tolerant lettuce varieties and Nile tilapia across a thermal range of 18-30°C in four-degree intervals. A heat tolerant variety was selected from each of the four main category of lettuce, resulting in four varieties of lettuce being used in this study (Parris Island, Butterhead, Black Seeded Simpson and Iceberg Batavian). Each of the 20 aquaponic systems used in this study consisted of a 114L fish tank, a 100L deep water culture hydroponic unit and a 19L biofilter. The experiment involved 4 treatments (18, 22, 26, 30°C) with five replicated systems. Eight tilapia (initial weight: 95.4 ± 0.95g) were stocked in each of the 20 fish tanks. Three replicates from each of the four varieties were used in each system (12 plants/ system). The experiment was conducted for five weeks. Water quality parameters were maintained at adequate levels for both tilapia and lettuce. At the termination of the study, lettuce was harvested and both wet and dry weights were collected. T ilapia were harvested and total biomass was recorded. Weight gain of tilapia was significantly better at 26 and 30°C than at 18 and 22°C. All four varieties of lettuce preformed significantly better at 30 °C than at 18 or 22 °C (p< 0.05) . T he current study suggests that a temperature of 26°C could be used when culturing tilapia and lettuce in an aquaponic system. However, a dditional studies are needed to determine if other heat-tolerant leafy greens are truly tolerant of higher temperatures.