Background <p>The declining fertility rate posed significant risks to social sustainability and development. However, few studies have explored the psychological factors and their potential mediating effects on the fertility intention for another child. Based on the theory of planned behavior (TPB), this study aimed to investigate the relationships among subjective norm (SN), perceived behavioral control (PBC), attitude (AT), and fertility intention (FI) for another child.</p> Methods <p>A multicenter cross-sectional survey was conducted from November to December 2022, using a sample of 455 women who had given birth from 3 districts in Shanghai, China. Structural equation modeling was employed to validate the proposed model. Multi-group analysis was conducted to explore differences across groups with different number of children.</p> Results <p>PBC (<i>β</i> = 0.212) and AT (<i>β</i> = 0.183) had positive direct effects on FI, while SN had a negative direct effect on FI (<i>β</i>=-0.123). PBC (<i>β</i>=-0.057) and AT (<i>β</i>=-0.035) mediated the impact of SN on FI respectively, functioning as sequential mediators (<i>β</i>=-0.028). The mediating effect of SN on FI accounts for 49.38% of the total effect. Among women with one child group, the path coefficient from PBC to FI was larger than that for women with multiple children (CR = -2.012).</p> Conclusions <p>SN exerted both direct and indirect negative effects on FI through the multiple mediating effects of PBC and AT, which also acted as sequential mediators. PBC had the strongest direct effect, compared with SN and AT. The effect from PBC to FI for women with one child was stronger than that for women with multiple children. Policy recommendations were provided to increase fertility intentions based on these results.</p>