Background Efforts to promote male partner involvement in the prevention of mother-to-child transmission (PMTCT) may inadvertently exploit gender power differentials to achieve programme targets. Methods We explored women’s relative power and perceptions of male partner involvement through interviews with postpartum Zambian women living with HIV (n = 32) using a critical discourse analysis. Results Women living with HIV reported far-reaching gender power imbalances, including low participation in household decision-making, economic reliance on husbands, and oppressive gendered sexual norms, which hindered their autonomy and prevented optimal mental and physical health during and after their pregnancy. When the husband was HIV-negative, sero-discordance exacerbated women’s low power in these heterosexual couples. Male involvement in HIV care was both helpful and hurtful, and often walked a fine line between support for the woman and controlling behaviours over her. Inequities in the sexual divisions of power and labour and gender norms, combined with HIV stigma created challenging circumstances for women navigating the PMTCT cascade. Conclusions Future programmes should consider the benefits and risks of male partner involvement within specific relationships and according to women’s needs, rather than advocating for universal male involvement in PMTCT. This work highlights the persistent need for gender transformative approaches alongside PMTCT efforts.