Background: The aim of the study was to compare the effect of season on the semen quality traits of Murrah and Nili Ravi buffalo breeding bulls. Methods: For a period of 5 years, a total of 855 ejaculation records of 17 buffalo breeding bulls, including Murrah (11) and Nili Ravi (6) buffalo bulls maintained at an organised farm, were analysed for various semen traits using least squares analysis. Result: Breed had a significant effect (p less than 0.01) on semen volume, consistency, mass activity (MA), total sperm count (TSC) and post thaw motility (PTM) and a non-significant effect on colour and initial motility (IM). In Murrah bulls, except for semen volume, the other parameters viz. consistency, MA, TSC and PTM were found to be significantly higher than Nili Ravi bulls. Season of semen collection had a significant effect on consistency, TSC and PTM whereas a non-significant effect on semen volume, colour, MA and IM was observed. During the summer season, overall consistency and TSC were higher, but PTM was found to be comparatively lower. Season and breed interaction had a significant effect (p less than 0.01) on consistency, TSC and IM while a non-significant effect on semen volume, colour, MA and PTM was observed. In Murrah buffalo bulls, a non-significant effect of season on consistency was observed whereas, in Nili Ravi bulls, a significantly higher consistency during summer and spring and; a significantly lower consistency during the rainy season was observed. In Murrah bulls, the highest TSC were observed during the rainy and summer seasons; whereas, in Nili Ravi bulls only during the summer season. In Murrah bulls, semen consistency, MA and IM were lower during the spring season; semen volume was lower during the prewinter season; total sperm count was lower during the winter season. In Nili Ravi bulls, semen volume was lower during summer; consistency, MA and TSC were lower during the rainy season; and IM was lower during the spring season. The PTM was lower during the summer season in both the breeds.