AimA new treatment interval for nivolumab administration at 480 mg every 4 weeks, in addition to 240 mg every 2 weeks, was approved in Japan in 2020. Using model‐based evaluation, it was speculated that the effects or safety of nivolumab do not differ between the two treatment intervals; however, real‐world data on nivolumab efficacy, safety, and economic impact are lacking. Accordingly, we aimed to examine the effects of nivolumab treatment intervals (2 weeks vs. 4 weeks) in terms of efficacy, safety, and economic impact in Japanese patients with cancer.MethodsWe retrospectively analyzed 126 patients treated with nivolumab. The patients were divided into two groups depending on whether they received nivolumab at 240 mg every 2 weeks (2‐week group) or 480 mg every 4 weeks (4‐week group).ResultsEfficacy results found no significant difference between the 4‐ and 2‐week groups considering median overall survival (p = 0.70) and median progression‐free survival (p = 0.57). The incidence of any grade and ≥ grade 3 immune‐related adverse events did not differ between the 4‐week and 2‐week groups (any grade, p = 0.13; ≥ grade 3, p = 0.36). Excluding drug costs, the 4‐week group had significantly lower medical costs than the 2‐week group (2‐week vs. 4‐week: mean, 94,659 JPY [679.0 USD] vs. 58,737 JPY [421.3 USD]; p < 0.05).ConclusionCollectively, our findings suggest that nivolumab 480 mg every 4 weeks may be more effective than nivolumab 240 mg every 2 weeks in terms of economic impact.