An endogenous amino acid 5-aminolevulinic acid (5-ALA) is a precursor of heme in the porphyrin synthesis pathway. It has been reported that 5-ALA synthase is decreased in the brains of patients with dementia, suggesting an association between cognitive function and 5-ALA. However, little is known about the role of 5-ALA in cognitive function. To address this issue, we evaluated learning and memory performance in the novel object recognition (NOR) test by using ddY mice (4-6-week-old). 5-ALA hydrochloride or vehicle was intracerebroventricularly administered 30 min before the training session. On the test day, 48 hours after the training session, 5-ALA (3 mM) -treated mice showed significantly higher ratio of contact time to novel object compared to the vehicle-treated mice. This result suggested that 5-ALA produced the enhancement of the object recognition memory in mice. Next, we examined a memory-related synaptic plasticity, long-term potentiation (LTP), of field excitatory post-synaptic potential (fEPSP) in area CA1 of the hippocampus. As the results, 5-ALA (300 mM) perfusion in the hippocampal slices significantly increased the slope of the fEPSP, suggesting the enhancement of the LTP. Based on these results, we propose that 5-ALA could have the enhancing effects on cognitive function in rodents.