Nivolumab, an antiprogrammed death-1 checkpoint inhibitor, has been approved for use in unresectable/metastatic renal cell carcinoma (RCC). Nivolumab-induced pneumonitis, a rare, but often severe and potentially life-threatening immune-related adverse event, has been reported, typically, early during the treatment. Due to its low incidence, more studies are needed to better elucidate this condition and its possible effects on cancer progression. We now present a 57-year-old Hispanic male patient with metastatic RCC-clear cell type who, after his 34th cycle of nivolumab (16 months after being on nivolumab), developed a late-onset, immune-related adverse event (IRAE) including a grade 3 pneumonitis, which resolved completely, clinically, and on serial lung imaging with steroids and drug discontinuation. His cancer remained stable with no progression for 18 months despite discontinuation of nivolumab which showed tumor progression resistance. This case report is aimed at providing further information regarding the rare phenomena of a late-onset IRAE, in particular, a grade 3 nivolumab-induced pneumonitis which also responded rapidly to treatment, as well as at discussing this immunotherapy's durable tumor suppressive effect and a possible associated factor to this phenomenon.