The use of antidepressants has been increasing resulting in its presence in the aquatic environment. This environmental release raises concerns on potential effects to non traget organisms that have physiological systems regulated by these pharmaceuticals. Sertraline (SER) is an antidepressant belonging to the serotonin reuptake inhibitor class (SSRIs) that has a high consumption rate. However, there is little knowledge about the toxicological effects of SER in aquatic ecosystems. Thus, this study aimed to evaluate the acute (0.1 up to 3000 µg.L^-1) and chronic (2 up to 100 ng.L^-1) effects of SER on zebrafish (Danio rerio) focusing on different endpoints, such as development (e.g. Fish Embryo Toxicity (FET) assay and heartbeat rate), behaviour (response to light/dark stimulus) and biochemical markers (e.g. associated with neurotransmission (AChE), antioxidant defenses (CAT and GST) and energy metabolism (LDH)). Overall, embryos demonstrated a high sensitivity to SER (e.g. promoting an increased heartbeat rate, increased sensitivity to light/dark stimulus at low concentrations and decreased sensitivity to higher SER concentrations. These findings support further research on the long-term effects of antidepressants such as sertraline to aquatic biota and new methodologies to efficiently remove them from the environment. Furthermore, it highlights potential effects to humans.