Introduction BK polyomavirus-associated nephropathy (BKPyVAN) is a well-known complication of kidney transplantation (KTx).The mainstay of prevention is reduction of immunosuppression upon detection of BK polyomavirus (BKPyV) viremia, which precedes BKPyVAN. However, this reduction may inadvertently increase the risk of alloimmunity particularly in patients with a high BKPyV load, where significant immunosuppression reduction is often necessary. This single-center, retrospective cohort study assesses the risk of de novo donor-specific antibodies (dnDSA) development and biopsy-proven acute rejection (BPAR) following high and low BKPyV viremia. Methods All patients who underwent KTx at Leiden University Medical Center between 2011 and 2020 were included. Patients were grouped according to high (maximum BKPyV serum load >10E4 copies/ml), low (maximum serum BKPyV load <10E4 copies/ml) and absent BKPyV viremia, and analyzed for the development of dnDSA and BPAR, using Cox regression. Results Of 1076 KTx recipients included, 108(10%) developed a BKPyV viremia with a maximum serum load below 10E4 copies/ml, whereas 121(11.2%) developed a BKPyV viremia exceeding 10E4 copies/ml. The risk of dnDSA development was higher in patients with a high BKPyV viremia, compared to patients without viremia (adjusted Hazard Ratio of 1.9(95% CI1.1-3.2, p=0.017). No significant difference in dnDSA risk was observed between patients with low and absent BKPyV viremia. Risk of BPAR did not differ between groups. Conclusion Our study shows that higher BKPyV loads in KTx patients are associated with a higher risk for dnDSA development, highlighting the importance of exploring additional strategies for the prevention and treatment of BKPyV infections in KTx recipients.