Patients with preexisting autoimmune disease (pAID) are generally excluded from clinical trials for immune checkpoint inhibitors (ICIs) for cancer due to concern of flaring pAID. In this multi-center, retrospective observational study, we compared safety of ICI combination (two ICI agents) versus monotherapy in cancer patients with pAIDs. The primary outcome was time to AEs (immune-related adverse events (irAEs) and/or pAID flares), with progression-free survival (PFS) and overall survival as secondary outcomes. Sixty-four of 133 patients (48%) received ICI combination and 69 (52%) monotherapy. Most had melanoma (32%) and lung cancer (31%). Most common pAIDs were rheumatic (28%) and dermatologic (23%). Over a median follow-up of 15 months (95%CI, 11-18 mo), the cumulative incidence of any-grade irAEs was higher for combination compared to monotherapy (subdistribution hazard ratio (sHR) 2.27, 95%CI 1.35-3.82). No statistically significant difference was observed in high-grade irAEs (sHR 2.31 (0.95-5.66),  = .054) or the cumulative incidence of pAID flares. There was no statistically significant difference for melanoma PFS between combination versus monotherapy (23.2 vs. 17.1mo,  = .53). The combination group was more likely to discontinue or hold ICI, but > 50% of the combination group was still able to continue ICI therapy. No treatment-related deaths occurred. In our cohort with pAIDs, patients had a tolerable toxicity profile with ICI combination therapy. Our results support the use of ICI combination if deemed necessary for cancer therapy in patients with pAIDs, since the ICI toxicities were comparable to monotherapy, able to be effectively managed and mostly did not require ICI interruption.