By establishing a labor-retirement model within China’s unique intergenerational support culture and one-child policy, this study provides evidence of the one-child policy’s early effect on individuals’ retirement decisions. This finding highlights a contradiction between the retirement intentions of the 1960s and 1970s generations, who are most affected by the one-child policy, and the delayed retirement policy of Chinese government. Utilizing data from the CHARLS 2011-2018 and employing OLS, IV, and fuzzy cohort DID estimation methods, we observe that only-child parents tend to retire at an earlier age compared to non-only-child parents. This early effect of the one-child policy on retirement decisions can be attributed to intergenerational support for children’s marriage and career, as well as the educational attainments of children, as confirmed by both theoretical and empirical analysis.