Background: Chlorpyrifos is an organophosphate pesticide that is widely used in the world. Exposure to chlorpyrifos is associated with some problems in cognitive functions, such as learning and memory. Caspase-3 is a cysteine protease that is activated in response to several apoptotic stimuli and triggers some proteolytic events, cell death, and neurodegeneration. Objectives: The aim of the present study was to clear potential mechanisms related to chlorpyrifos neurotoxicity through caspase-3 alteration and passive avoidance memory function. Methods: Male adult rats were randomly divided into the control, sham, and chlorpyrifos groups (eight rats in each group). The chlorpyrifos group received an intraperitoneal injection of chlorpyrifos (3 mg/kg/5 days) dissolved in dimethyl sulfoxide for two consecutive weeks. The caspase-3 levels in the hippocampus were assessed by the western blot technique, and also the passive avoidance task was used for memory evaluation. Results: Our findings showed that chlorpyrifos treatment markedly increased caspase-3 levels in the hippocampus and also increased the time spent in the dark chamber 24 h and one week after receiving foot shock in the chlorpyrifos group. Conclusions: Organophosphate pesticides exposure can impair passive avoidance memory, and high levels of caspase-3 in the hippocampus are proposed as a possible reason for neuronal toxicity and memory impairment.