Data on ages at first mating and first calving of Murrah buffaloes to identify the effect of various non-genetic factors on these traits. Period and season were the fixed environmental effects considered for both the traits studied. The overall least-squares means for ages at first mating and calving were 1222.3 ± 11.0 and 1578.7 ± 20.3 days respectively. Period had highly significant (P<0.01) influence on both the traits studied, whereas, season had significant (P<0.05) effect on age at first calving alone. The age at first calving was the lowest in period 1 (1979 to 1982), which was significantly (P<0.05) different from the rest. The heritability estimates for ages at first mating and calving were 0.0499 ± 0.07 and 0.1648 ± 0.12 respectively. The genetic correlation of age at first calving with peak yield, days to attain peak yield, 305-day milk yield, lactation length, lactation milk yield, milk yield per day of lactation, service period, calving interval, dry period and number of services per conception were -0.214 ± 0.32, 0.013 ± 0.31, 0.089 ± 0.33, 0.584 ± 0.47, 0.166 ± 0.35, -0.177 ± 0.30, 0.576 ± 0.53, 0.563 ± 0.55, 0.276 ± 0.49 and 0.944 ± 0.83 respectively. The study revealed that the ages at first mating and calving observed in Murrah buffaloes at coastal region of Tamil Nadu is comparable to those reported in its breeding tract and elsewhere in India. A negative genetic correlation between age at first calving and milk yield per day of lactation indicated that the selection based on milk yield per day of lactation would lead to reduction in age at first calving with consequent increase of milk yield per day of lactation in future generations.