Abstract Introduction Anti-programmed cell death-1 (PD-1) and anti-programmed cell death ligand-1 (PD-L1) monotherapies have shown promising clinical activity in advanced cancers. Many studies of immune-related adverse events (irAEs) have been reported. Although, the safety and efficacy of PD-1/PD-L1 blockade in patients with preexisting positive antinuclear antibodies (ANA) and autoimmune disease (AD) remains unclear. Methods: 216 patients who received nivolumab, pembrolizumab, atezolizumab or durvalumab for unresectable advanced cancers between September 2014 and December 2018 were retrospectively identified. The patients were divided into the positive (ANA titers≥1:80) and negative (titers≤1:40) ANA groups. Development and characteristics of irAEs, the response rate (RR) and disease control rate (DCR) were estimated. We also focused on the patients with preexisting AD and assessed their clinical courses. Results: 17 out of 190 patients had positive ANA. 8 patients developed irAEs of any grade in the positive ANA group while 65 developed in the negative group, which showed no significant difference among the two groups. No significant differences were shown in the development of endocrine, pulmonary and cutaneous irAEs, while the presence of positive ANA was significantly higher in patients who developed colitis (3/17) than in patients who did not (2/173, P