Psychiatric drugs have been increasingly prescribed and, due to a reduced efficiency of waste water treatment plants, their environmental levels have been increasing in aquatic ecosystems. Fluoxetine, selective serotonin reuptake inhibitor (SSRI), is among the pharmaceuticals most commonly detected in the aquatic environment. In this work, the effects of fluoxetine on zebrafish (Danio rerio) juveniles were evaluated assessing biochemical endpoints (e.g., effects on biotransformation – glutathione S-transferase (GST), neurotransmission – acetylcholinesterase activity (AChE), energy metabolism - lactate dehydrogenase (LDH) and antioxidant defenses - glutathione peroxidase (GPx)) and behavior (swimming behavior, social behavior and thigmotaxis) after 21 days exposure to 0 (control) 0.1, 1 and 10 µg/L. Overall, fluoxetine induced no significant effects on neurotransmission and energy metabolism. The antioxidant enzyme glutathione peroxidase (GPx) and the phase II biotransformation enzyme GST presented decreased activities after exposure to 10 µg/L. In terms of behavior, exploratory and social behavior was not affected. However, the response to light and dark stimuli was affected, with fish exposed to the highest concentration swimming longer distances in the dark period. All fluoxetine tested concentrations induced an increase of aggressive behavior. Overall, the data show that juvenile fish chronically exposed to fluoxetine may exhibit behavioral changes, affecting their ability to respond to environmental stressors and the interaction with other fish.