Objective: The objective of the study was to compare mean Amniotic Fluid Index (AFI) in maternal oral hydration with routine hydration in third trimester oligohydramnios. Study design: Randomized control trial. Settings: Department of Gynea/Obs Faisalabad Medical University, Faisalabad. Duration of study: 6 months from 1 st June to 30 th November 2016. Methodology: A total of 80 cases (40 in each group), were included in the study, Group A was oral hydration group and was enquired about daily water intake. They are bound to take 2 liters of water in addition to their daily intake for 7 days. Group B was routine hydration group and continued to drink water determined by thirst and followed up on OPD basis according to the hospital protocol. Ultrasonography was done by radiology department and reported by radiologist after completion of 7 days and revised amniotic fluid index was noted. All the information was recorded on proforma. Results: In this study, (40 in each group), 65%(n=26) in Group-A and 57.5%(n=23) in Group-B were between 18-30 years and 35%(n=14) in Group-A and 42.5%(n=17) in Group-B were between 31-45 years of age, mean+sd was calculated as 27.88+5.40 years and 28.80+5.72 years respectively, pre-treatment mean AFI volume was in-significant between the two groups. Post-treatment mean AFI volume was recorded as 6.83+0.81 in Group-A and 5.05+0.75 in Group-B, p value was calculated as 0.001 which shows significant difference between the two groups. Conclusion: We concluded that oral hydration appears to be significantly increased in mean AFI as compare to routine hydration in third trimester oligohydramnios, this therapy can be used instead of expectant management or invasive techniques in patients of third trimester oligohydramnios.