Sarcoid-like reactions associated with the immunotherapy are rare adverse events. The first case of a sarcoid-like reaction related to the use of checkpoint inhibitors was described in 2008 in a patient with melanoma receiving ipilimumab therapy. The gastrointestinal tract is most frequently affected, with less frequent involvement of mediastinal lymph nodes and the lungs, and very rarely the thyroid gland. These changes present significant diagnostic challenges, as it is impossible to differentiate a sarcoid reaction from the progression of the underlying oncological disease without morphological verification. Moreover, a sarcoid reaction can develop in parallel with the progression of the primary disease, further complicating the diagnosis. In the presented case, a patient with progressive melanoma developed mediastinal lymphadenopathy and lung involvement with severe respiratory symptoms 10 months after initiating immunotherapy. To confirm the diagnosis, transbronchial lymph node biopsy and cryobiopsy of lung tissue were performed. Histological examination revealed epithelioid cell granulomas, confirming the diagnosis of a sarcoid-like reaction and enabling the initiation of pathogenetic therapy with methylprednisolone. However, in our case, there were two relapses of sarcoidosis 6 months and a year after discontinuation of immune therapy against the background of discontinuation of steroid treatment, which may indicate the initial induction of sarcoidosis by immune therapy with further chronization of the process. Thus, given the increasing role of immunotherapy in oncology, knowledge about the potential development of various immunopathological reactions is important for determining treatment strategies. This clinical case highlights the importance of raising awareness among clinicians about the possibility of such complications during immunotherapy.