Patients who develop malignancy after kidney transplantation typically undergo a reduction in immunosuppression and referral to an oncologist for chemotherapeutic considerations for the management of their malignancy. Traditional cytotoxic chemotherapy agents can result in kidney transplant injury, but the decision about which agents to be used has largely been determined by oncologists without the involvement of nephrologists. More recently, several classes of drugs with immunomodulatory actions have been approved for the treatment of cancer, including multiple myeloma. Activation of the immune system against malignant cells may have unintended consequences in solid-organ transplant recipients, who require suppression of the immune system to avoid transplant rejection. In this report, we present a case of acute kidney transplant rejection in a 65-year-old woman following administration of the newer immunomodulatory agent lenalidomide for the treatment of multiple myeloma. A greater awareness of the mechanisms of newly introduced chemotherapy agents and discussion with the treating oncologist and patient are paramount in caring for patients who develop malignancy following transplantation.