Sertraline (“Zoloft”) is a selective serotonin reuptake inhibitor (SSRI) suspected of causing developmental abnormalities in some aquatic organisms at environmentally relevant concentrations. SSRIs have been detected downstream from wastewater treatment plants, but the risks associated with environmental exposure have not been well documented. We tested the effects of sertraline on development of Wood Frog (Lithobates sylvaticus) larvae. Tadpoles hatched from wild-collected egg masses were exposed to concentrations of 0, 0.1, 1.0, or 10.0 μg/L of sertraline through metamorphosis. We tracked tadpole development using image analysis (452 digital images) to estimate mass periodically during the tadpole stage, and we also recorded mass at metamorphosis. Time to metamorphosis did not differ between treatments, but sertraline-exposed tadpoles grew less when raised among conspecifics. However, this effect was not detected when the study was repeated with tadpoles raised individually. This indicates that the effects of sertraline and other SSRIs may be enhanced when tadpoles are raised under more stressful conditions.