We report some basic circadian characteristics in Mus terricolor, the nocturnal pygmy field mouse. Both male and female M. terricolor entrain well to a 12:12 light:dark schedule. Activity is completely nocturnal in distribution in LD. ρ and α in LD differ significantly between males and females. Free-running circadian locomotor activity rhythm in DD was 23.69 h (males) and 23.46 h (females). In LD, ψ was −0.20 h and −0.15 h in males and females, respectively. Rhythms were accurate (6.02 in males/7.30 in females [h−1]) and precise (4.83 in males /4.74 in females [h−1]). Fifteen-minute perturbations with ∼70 lux white light in DD led to predictable phase advances and delays. Mus terricolor took ∼7 days to re-entrain to a 6 h advance in the ambient light schedule, with rapid resynchronization to a 6 h phase delay. These results indicate that M. terricolor is a good model animal for in-depth research in circadian biology.