Background: The incidence of melanoma increases with age, however, elderly patients remain under-represented in landmark immunotherapy trials for metastatic melanoma. This study aims to investigate the impact of age on efficacy and toxicity of immunotherapy, and complications of immunosuppression to treat toxicity. Methods: A multicentre retrospective study involving centres in Australia [Gold Coast University Hospital, Cairns Base Hospital, Townsville University Hospital] was performed to compare the efficacy and toxicity of immunotherapy in metastatic melanoma in patients ≥70 years versus patients < 70 years treated between 2015 and 2019. Data collected included: baseline demographics, PFS, OS, Grade 3 or higher (Gr3+) adverse events as per CTCAEv5, adverse events leading to discontinuation, duration of steroids used to treat toxicity and complications secondary to steroids. Comparison of survival outcomes between the groups was calculated using Kaplan Meier, Log rank test and multivariate Cox regression analysis. Fisher exact test was used to determine differences in toxicity between the two groups. Results: A total of 229 patients were included with 106 patients ≥70years and 123 patients < 70 years. Baseline demographics were similar. Dual immunotherapy (ipilimumab + nivolumab) was less commonly used in patients ≥70years [13 v 38% p < 0.001]. Although the median PFS was numerically higher amongst ≥70years [10.8 v 6.9months p = 0.99], the landmark PFS was not [3yr PFS: 31 v 39%; 4yr PFS: 22 v 39%]. The median OS was similar in patients ≥70 years v < 70years [27.5 v 28.7 months p = 0.91], with similar landmark survival [3yr OS: 46 v 49%; 4yr OS: 42 v 49%]. Age was not associated with a difference in overall survival on multivariate analysis. There was no increase in Gr3+ adverse events in patients ≥70 years [22 v 21% p = 1.00] or discontinuation rates [26 v 20% p = 0.35]. There was one death in a patient < 70years secondary to colitis. There was a significantly higher rate Gr3+ adverse events in ≥70years patients receiving dual immunotherapy [71 v 35% p = 0.029] and a similar rate of Gr3+ adverse events with PDL1 inhibitors [13 v 11% p = 0.7]. Median duration of steroids was similar in both group [15 v 17wks], as was the median duration of high dose steroids defined as greater than 10mg of prednisone [5 v 6wks]. Complications of steroids was numerically higher in the elderly population [42 v 25% p = 0.15]. The most common adverse event to immunosuppression was infection. Conclusions: Patients ≥70years received similar benefit from immunotherapy in comparison to their younger counterparts. Toxicity related to PDL1 inhibitors was similar in both groups and was higher in patients ≥70years receiving dual immunotherapy. Patients ≥70 years had a clinically significant higher rate of complications secondary to steroids.