There have been studies that demonstrate the impact of sleep on both implicit and explicit memory. Of particular interest is that sleep has been shown to aid memory consolidation. This holds some implication for students, most of whom sleep for considerably very little amount of time, whereas they require sufficient amount of sleep to consolidate memory for material learned during the day. This study was therefore designed to investigate the possible impact of sleep on the academic achievement of undergraduate students. The study participants were 300 undergraduate students drawn from about twenty Department of a private university in Nigeria. 152 of the participants were female and the rest were male. The School Sleep Survey Habit Scale previously validated in Nigeria by one of the authors (IDO) was used to measure sleep habit, while academic performance was measured as self-reported grade. The result of Analysis of variance using SPSS XX showed a significant effect of Sleepiness on Academic Performance F (8, 211)=3.73, P<.01, and on Cumulative Grade Point Average, F (4, 190) = 3.82, P<.005. The study also showed that stimulant intake significantly impacted on Sleep habit. It was concluded that to enhance student's academic achievement counseling centres should endeavour to include sleep in their orientation programme for students. Besides, it would be necessary not to cram up the programme in such a manner that would rob the students of adequate rest and sleep.