A negative association between gender equality and intimate partner violence against women (IPVAW) is widely reported in the literature. But does this effect extend to when attitudes towards both gender equality and IPVAW, rather than their actual levels or occurrence, are being studied? Are people less likely to justify IPVAW when they support gender-equal opportunities? Also, does ethnicity moderate this relationship? This study addresses these questions using nationally representative Nigerian samples from the World Values Survey (n = 1,106). Bivariate analyses using ANOVA and Chi-square tests, and multivariate analysis using logistic regression, were performed to test relationships. Accounting for covariates, the findings only marginally supported the hypothesised negative effect of gender equality support on IPVAW justification (average marginal effect [AME] = −0.12, p = .058), partly because ethnicity moderates this effect. The probability of justifying IPVAW significantly reduced with increasing support for gender equality among the Yoruba (AME = −0.43, p < .001) and ethnic minority groups (AME = −0.45, p < .001), but not among the Igbo or Hausa/Fulani. When examined by gender, the negative relationship was significant only for women (AME = −0.22, p < .05); strengthened when the woman is Yoruba (AME = −0.62, p < .001) or ethnic minority (AME = −0.70, p < .001), and weakened when the woman is Igbo (AME = 0.38, p < .05). These results highlight the importance of considering culture as affecting the relationship between support for gender equality and IPVAW justification in Nigeria for targeted interventions in changing attitudes supporting IPVAW.