This study was conducted in 36 multiparous Cross Bred Jersey cows at Tirunelveli and Thoothukudi districts of Tamil Nadu state in India from the day of calving up to day 45 post-partum with the aim to assess the effect of an immunomodulatory diet on postpartum uterine involution, follicular dynamics, and reproductive performance by using trans-rectal ultrasonography (TRUS). Animals were divided into three groups on the basis of feeding viz. Group I (n=12), as control, Group II (n=12), was fed with conventional balanced feed and Group III (n=12), was fed with an immunomodulatory diet with flax seed and the inclusion of organic minerals and supplements. TRUS was performed on day 0, 7, 14, 21, 28, 35, and 42 to assess the uterine involution and elimination of bacterial contamination. Further, USG was also performed on day 7, 10,13,16,19, 22, 25, 28, 31, 34, 37, 40, 43, and 45 to assess follicular dynamics. All animals were subjected to estrus synchronization by using the CIDR protocol and performance parameters were recorded. This study revealed that uterine involution was significantly faster (P<0.01) in Group III than in Group I and II. PMN % was significantly lower (P<0.01) in Group III followed by Group II and I. Further, the emergence of 1st Follicular wave and ovulation was significantly (P<0.01) earlier in Group III than in Group I and II, and the intensity of estrum and conception rate was significantly higher (P<0.01) in Group III as compared to Group I and II. The number of AI per conception was significantly lower (P<0.01) in animals fed with immunomodulatory feed than in the other two groups.