Background Immune checkpoint inhibitor (ICI) can cause severe and sometimes fatal immune-related adverse events (irAEs). Since these irAEs mimick immunological disease, a female predominance has been speculated on. Nevertheless, no demographic or tumour-related factors associated with an increased risk of irAEs have been identified until now. Methods Risk ratios of severe (grade ≥3) irAEs for age, sex, WHO performance status, number of comorbidities, stage of disease, number of metastases and serum lactate dehydrogenases (LDH) were estimated using data from anti-PD1-treated patients with advanced melanoma in the prospective nationwide Dutch Melanoma Treatment Registry. Results 111 (11%) out of 819 anti-programmed cell death 1 treated patients experienced severe irAEs. Patients with non-lung visceral metastases (stage IV M1c or higher) less often experienced severe irAEs (11%) compared with patients with only lung and/or lymph node/soft tissue involvement (stage IV M1b or lower; 19%; adjusted risk ratio (RR adj) 0.63; 95% CI 0.41 to 0.94). Patients with LDH of more than two times upper limit of normal had a non-significantly lower risk of developing severe irAEs than those with normal LDH (RR adj 0.65; 95% CI 0.20 to 2.13). None of the other variables were associated with severe irAEs. Conclusion In patients with melanoma, more advanced disease is associated with a lower rate of severe irAEs. No association with sex was found.