The grasscutter (Thryonomysswinderianus) holdspromise as a source of increased protein for populations of Sub-Sahara African countries. It is inexpensive to feed and features the feed utilization characteristics of ruminants and monogastrics. It is nocturnal in its activities, especially feeding. This experimentwas carried out to determine the effect of daylight hours or photoperiod on growing grasscutters under intensive rearing conditions. The effect of daylight hours on growing grasscutters was determined using sixteen 8-months old femalegrasscutters. The grasscutters were separated into four groups and allotted to four treatments of varying daylight hours. The treatments included; zero (0) hours of daylight and twenty four (24) hours (6.00 am-6.00 am) of darkness (0L:24D), six antemeridiem (am) hours (6.00 am-12.00 noon) of daylight and eighteen (18) hours (12.00 noon-6.00 am) of darkness (6L(am):18D), six post-meridiem (pm) hours (12.00 noon-6.00 pm) of daylight and eighteen (18) hours (6.00 pm-12.00 noon) of darkness (6L(pm):18D) and twelve (12) hours (6.00 am-6.00 pm) of daylight and twelve (12) hours (6.00pm-6.00am) of darkness (12L:12D).Allgrasscutters were fedadiet containing 2200kilocalories metabolizable energy per kilogram (KcalME/kg) and crude protein (CP) level of 20%. Cassava root meal and wheat offalwere the main sources of energy, while soybean meal was the main source of protein in the diets. Elephant grass was fed as basal diet.The results showed thatforage, concentrate (diet) and total feed intake, and daily weight gain were significantly (P<0.05) higher under the 6 post-meridiem hours of daylight and 18 hours of darkness (6L(pm):18D) than under other conditions. It was, therefore, concluded that the optimum daylight conditions required for the rearing of growing grasscuttersare the six (6) hours of post-meridiem daylight, followed by eighteen (18) hours of darkness.