Mating in harvest mice, Micromys minutus, was observed by introducing males to females that were in cyclic estrus (CE), that had just delivered pup (postpartum estrus, PPE), or that were not pregnant but lactating after PPE (lactational estrus after PPE: LEAP). Copulation leading to pregnancy and weaning of pups occurred at every trial for CE (n = 11) and for PPE (n = 6). In LEAP, estrus with copulation and subsequent pregnancy occurred at each of seven mating trials. At six of these trials, weaning of pups occurred as well. The mean length of gestation (± SE) was 17.55 ± 0.12 days for mating in CE, 17.56 ± 0.17 days for mating in PPE, and 17.75 ± 0.20 days for mating in LEAP. Generalized linear mixed modeling found no significant effect of the type of estrus at mating on gestation length. The number of pups conceived from mating in the three estrus types did not significantly differ. Mating and pregnancy in the lactation period (PPE and LEAP) had no significant effect on the number of pups at weaning that were suckling during mating.