Ketamine is a rapid-acting antidepressant often accompanied with different cognitive side effects. Previous research has generated mixed results regarding its effects on distinct types of memory. Here, we investigated the effects of an antidepressant dose (10 mg/kg) of ketamine on encoding, retrieval, and modulation processes in an implicit and an explicit memory task in adult male Wistar rats (n = 60). Ketamine (IP) was administered 30 minutes either before the acquisition, retrieval, or extinction phase of auditory fear conditioning (implicit task). Similarly, different groups of animals received ketamine injections 30 minutes prior to the training, probe trial, or reversal training in the Morris water maze (MWM; explicit task). We found that administering ketamine before the retrieval or extinction phases of fear conditioning impaired memory recall, as evidenced by the relatively sustained freezing levels during extinction trials. In MWM, the escape latency of the vehicle group significantly decreased on the second day of reversal training compared to the ketamine-receiving groups, suggesting that ketamine may exert a transient ameliorating effect on spatial memory. These findings altogether demonstrate that the antidepressant dose of ketamine may impede memory modulation in implicit memory but initially enhance it in explicit memory paradigms. This indicates differential effects of ketamine on amygdala- and hippocampus-dependent memory processes.