Abstract Background It is unclear whether inflammatory bowel diseases (IBDs) affect the phenotype and severity of co-occurring immune-mediated inflammatory diseases (IMIDs). We aimed to investigate the characteristics of IMIDs in relation to co-occurring IBD. Methods We conducted a systematic review of Medline and EMBASE databases from inception to September 2020. We identified studies reporting the phenotype, severity, or disease course of IMIDs among patients with or without co-occurring IBD. A meta-analysis was conducted using random effects models. Results The electronic search yielded 13 220 studies that we narrowed down to 73 eligible studies for full-text review, including 42 on primary sclerosing cholangitis, 12 on axial spondyloarthropathies, and 8 studies on psoriasis. In primary sclerosing cholangitis, IBD was associated with less frequent involvement of extrahepatic bile ducts (risk ratio [RR], 0.50; 95% confidence interval [CI], 0.33-0.75), longer liver transplantation–free survival (hazard ratio, 0.70; 95% CI, 0.60-0.82), and no increased risk of cholangiocarcinoma (RR, 0.88; 95% CI, 0.59-1.31). Patients with axial spondyloarthropathies and co-occurring IBD were characterized by an increased risk of dactylitis (RR, 2.06; 95% CI, 1.24-3.42), a lower Bath Ankylosing Spondylitis Radiology Index (mean difference [MD] = -2.28; 95% CI, -3.26 to -1.30), and better Schober’s test results (MD = 1.07; 95% CI, 0.64-1.49). Psoriasis and co-occurring IBD was associated with reduced disease severity (RR, 1.41; 95% CI, 1.02-1.96) and less frequent presentation in nails (RR, 0.14; 95% CI, 0.05-0.42), with no apparent impact on psoriatic arthritis (RR, 0.94; 95% CI, 0.27-3.31). Conclusions This systematic review with meta-analysis found IBD is associated with a distinct disease phenotype among the IMIDs investigated. Our findings emphasize the importance of multidisciplinary approaches to patients with co-occurring IMIDs and IBD.