Tacrolimus (FK506) and cyclosporine, synonymous with immunosuppressive therapy in organ transplantation, are not spared of potential adverse effects such as nephrotoxicity. We retrospectively compared their effects on cGFR in a post-OLT pediatric population. cGFRs of 32 patients from the LTUNUHS either on tacrolimus (group 1) or cyclosporine (group 2) from pretransplantation, transplantation and 3, 6, 9, 12, 18, 24, 30 and 36 months post-transplantation were compared. 95% CI and p-values were calculated for comparison with p < 0.05 considered significant. Longitudinal data analysis revealed no significant cGFR difference between groups 1 and 2 (p = 0.154). However, there was a significant difference in cGFR with time after transplantation (p < 0.0001). The mean difference score between both treatment groups was 277.92 (95% CI = 88.13-643.97). The survival rate post-OLT was 84.4%. In this retrospective sex-matched case controlled study of LTUNUHS patients, there was no difference between tacrolimus and cyclosporine on renal function. However, there was significant difference in cGFR with time post-OLT (p < 0.0001). The reason for this observation could be multifactorial.