Background. Checkpoint inhibitors are now frequently used for oncologic conditions. The impact of these therapies in solid organ transplant recipients was not assessed in clinical trials. Subsequent case reports highlight the major detrimental interactions of checkpoint inhibitors and the high risk of allograft rejection with their use. Patient outcomes have not been assessed in long-term follow-up. Methods. We conducted a retrospective review of kidney transplant recipients with metastatic cancer who received checkpoint inhibitors at a single center between April 2015 and May 2018. Results. Six kidney transplant recipients with metastatic cancers that were not responding to first-line treatments met study criteria. These include 2 with squamous cell cancers, 2 with melanoma, 1 with renal cell cancer, and 1 with adenocarcinoma of the lung. Four patients received anti-programmed cell death protein-1 (PD-1) antibody and 2 received a combination of anticytotoxic T-lymphocyte-associated protein 4 and anti-PD-1 antibodies. Three out of 6 patients developed acute kidney injury. Two were biopsy-proven acute rejections with subsequent graft failures. The third was attributed to rejection, but improved after discontinuing the checkpoint inhibitor. Five out of 6 patients had cancer progression and only 1 patient had remission. Conclusions. Providers and patients need to be aware of the high risk of rejection and the poor remission rate with the use of checkpoint inhibitors in kidney transplant patients. More research is warranted to assess the optimal maintenance immunosuppression during the use of checkpoint inhibitor therapy that would not diminish the chances of remission.