This study aimed to investigate the long-term effect of both paternal and maternal warmth on children’s subjective well-being and explore the intervening role of parent–child relationships and the moderating effect of child gender on above effect in Chinese families. A total of 1322 children (Mage at Time 1 = 10.30 years, SD = 0.33; 49.7% boys) and their parents (Mage of fathers at Time 1 = 41.63 years, SD = 5.22; Mage of mothers at Time 1 = 39.11 years, SD = 4.47) participated the questionnaire survey at two time points, 1 year apart. Parental warmth was reported by both fathers and mothers at the first time point, while parent–child relationship and subjective well-being were self-reported by children at the first and second time points. The results of our latent variable structural equation modeling revealed that parental warmth at Time 1 positively predicted children’s subjective well-being at Time 2 via both parents’ own relationship with their child and their spouse’s relationship with their child after controlling the children’s subjective well-being at Time 1. Furthermore, there was no child gender difference in the indirect effect of parent–child relationships on the long-term effect of parental warmth on children’s subjective well-being. These findings provide significant implications for the improvement of children’s subjective well-being and suggest that more parental warmth from both fathers and mothers can help build positive parent–child relationships, thereby further promoting mental health development among children in China.