Abstract: The present study was designed to investigate the effects of GnRH injection during early postpartum on uterine involution, length of postpartum period, number of services per conception, days open and calving interval in cross-bred Sudanese dairy cows. A total of 20 cross-bred dairy cows were used to examine the effects of GnRH on the above mentioned parameters. The cows were grouped into 2 groups: A (n = 15) and B (n = 5). Group A was further grouped into 3 subgroups (5 cows each). The first group was given a single injection of GnRH (200?g) i.m on day 7, the second and third groups were given the same dose of GnRH on day 14 and day 21, respectively. Cows in group B were employed as untreated control. The results of the present study showed that, injection of GnRH during the third week postpartum has no effect on uterine involution, whereas, injection of GnRH during the first or the second week postpartum significantly reduced (P<0.005 and P<0.05, respectively) the time taken for uterine involution, compared to the control. The postpartum period of the cows treated with GnRH as early as first, second or the third week postpartum was significantly (P<0.05) shorter as compared to the control. The shortest postpartum period was achieved by injecting GnRH during the third week. The cows received an injection of GnRH during the first, second or the third week postpartum has a similar number of services per conception (1.00?0.00) which was significantly different (P<0.04) from that of the control (1.40?0.20). Moreover, their days open and calving interval were significantly reduced (P<0.001) compared to that of the control. It is concluded that the use of GnRH during early postpartum improves the reproductive efficiency of cross-bred dairy cows.