Background: BK polyomavirus (BKV) induces allograft malfunction in renal transplant recipients (RTRs) and it could cause loss of the allograft, however, this virus does not cause any harm among healthy subjects. Aims: This study was conducted to determine and compare the frequency of BK viremia between RTR and healthy subjects, and to find out its risks and its relation to their renal function. Settings and Design: This was a case–control study. Subjects and Methods: A total of 206 blood samples were collected from (106) RTRs within the first 2 years posttransplantation from the center of kidney diseases and transplantation, and (100) nonrenal transplant samples (healthy blood donors from the Iraqi Blood Donation Center in the Medical City of Baghdad. The large tumor antigen region of BKV was amplified by a real-time polymerase chain reaction. Statistical Analysis Used: Frequencies, percentages, Chi-square-test, odds ratio (OR), and confidence interval were used for statistical analysis by SPSS v. 28 (IBM ,USA). Results: BKV was positive in 23 (21.7%) of RTR patients and 8 (8.0%) of control, which is statistically significant P = 0.005. RTR patients under tacrolimus (TAC) were at a higher risk, to had BKV viremia (P = 0.05). However, there was no significant difference neither in relative risk (OR = 0.904) nor the distributions (P = 0.839) regarding serum creatinine levels. Conclusions: A significantly higher BK viremia among RTR and increasing risk of reactivation with TAC immunosuppression should warn the nephrologists about the risk of this immunosuppression regimen on the renal allograft.