Background: Long-term outcome in renal transplantation is heterogeneous, and predicting success is challenging. Serum β2-microglobulin (β2MG), a novel marker of kidney function, predicts mortality and kidney failure in the general population, and its elevation following transplantation is a marker of acute rejection. Objective: To determine whether serum beta-2-micro-globulin one three-year post-transplant period could predict the decline in GFR over a follow-up period of six months. Patients and methods: This study was carried out at the National Institute of Nephrology and Urology, Cairo, Egypt. The patients were subjected to different demographic, clinical, biochemical, ultrasonographic, and endoscopic findings. In this study, 42 primary kidney transplant recipients were included. Results: The results showed a significant increase in serum β2-microglobulin level between renal transplant recipients with unstable kidney functions in comparison to renal transplant recipients with stable kidney function. The results showed serum β2-microglobulin level could be a good predictor of renal graft outcomes. Measurements of serum levels of beta 2 micro-globulin could be more sensitive and more specific than serum creatinine as renal function tests for early prediction of graft dysfunction. Conclusion: In this study, we found an association between serum level of β2MG in the late post-transplant period and a subsequent decline in kidney allograft function within a short time-frame. The overall results show that a higher serum level of β2MG after a single measurement at different intervals of the late post-transplant period independently predicts the lower eGFR. Thus, higher serum β2MG is a risk factor for graft function, particularly with longer follow-up.