Plantain, a staple diet of tropical Africans, contains serotonin with its precursor tryptophan in significant amounts. Serotonin, a neurotransmitter, is believed to have effects on memory. Thus, this study was aimed at assessing the effect of chronic consumption of plantain diet that contains serotonin on learning and memory in mice. Thirty mice were fed with rodent chow (control), 50% plantain diet per body weight and another group with 100% plantain diet for thirty days. Their learning and memory were checked through their ability (in the acquisition and reversal training processes) to locate the hidden platform model of Morris water Maze apparatus. It was observed that learning (on days of acquisition training) was improved in the 50% and 100% plantain diet-fed mice when compared to control (p<0.05 respectively). The trend was similar during reversal training where memory was improved in the 50% and 100% plantain diet-fed mice when compared to the control (p<0.05 & p<0.001 respectively). Serotonin concentration in mice following plantain consumption was measured in the brain of the mice. In Conclusion, chronic consumption of plantain diet increased serotonin concentrations in the brain of mice. It also improved learning and memory.