Despite numerous observational studies indicating an increased risk of cutaneous melanoma (CM) due to childhood sunburn, no studies have established a definitive cause‐and‐effect relationship. Therefore, our objective was to employ a Mendelian randomization (MR) design to explore a possible causal association between childhood sunburn and the risk of CM. To investigate the causal relationship between childhood sunburn and CM, we used large‐scale genetic summary‐level data from genome‐wide association studies (GWAS), including childhood sunburn (n = 346,955) and CM (n = 262,288), building upon previous observational studies. In the analysis, we mainly used the inverse‐variance weighted (IVW) method of the random effects model, supplemented by the weighted median method and MR‐Egger method. The results of the IVW method demonstrated that genetically predicted childhood sunburn was significantly associated with higher odds of CM, with an odds ratio (OR) of 2.418 (95%CI, 1.426–4.099; p = .001). The weighted median method and MR‐Egger regression also demonstrated directionally similar results (both p < .05). Furthermore, both the funnel plot and the MR‐Egger intercepts showed the absence of directional pleiotropy between childhood sunburn and CM. Our study offers potential evidence linking genetically predicted childhood sunburn with CM, underscoring the need for individuals with a history of childhood sunburn to be extra vigilant regarding the occurrence of CM. This article explores the potential causal relationship between childhood sunburn and the risk of melanoma through a Mendelian randomization design. The results suggest a positive correlation between genetically predicted childhood sunburn and the risk of melanoma. Therefore, this study provides potential evidence linking childhood sunburn to melanoma and suggests that individuals with a history of childhood sunburn should be more vigilant in preventing melanoma.