Background <p>Malaria in pregnancy and its devastating consequences can be prevented with the use of adequate doses of intermittent preventive treatment with sulfadoxine-pyrimethamine (IPTp-SP). Missed opportunities for IPTp-SP are defined as pregnant women who attended four or more antenatal care (ANC) visits but did not receive the recommended three or more IPTp-SP doses during ANC. Missed opportunities for IPTp-SP remain high, despite modest antenatal care (ANC) coverage in Nigeria. However, there is a paucity of evidence on the level of inequalities of missed opportunities for IPTp-SP use among pregnant women in Nigeria. This study aimed to assess the prevalence and inequalities of missed opportunities for IPTp-SP of malaria among pregnant women in Nigeria.</p> Methods <p>A secondary analysis of the 2018 Nigeria Demographic and Health Survey (DHS) datasets was conducted. The study analysed data on 12,498 women aged between 15 and 49&#xa0;years with a live birth two years before the survey who were recruited based on a stratified two-stage cluster sampling method. The prevalence and socioeconomic disparities in IPTp-SP missed opportunities were determined using descriptive analysis, and a Sankey diagram was developed to facilitate the identification of patterns of missed opportunities for IPTp-SP. Pearson's chi-squared test for heterogeneity and logistic regression analysis were used to assess inequalities and intersectionality of variables, respectively.</p> Results <p>The study revealed a high prevalence (75%) and a pro-rich/pro-educated inequality of missed opportunities for IPTp-SP among pregnant women in Nigeria. Among women who attended four or more ANC visits, 75% received fewer than three IPTp-SP doses; this represents 42.5% of the total sample analyzed in this study. It showed an inverse relationship with prevalence increasing as education and wealth decrease. The prevalence of worst-case scenario (&lt; 4 ANC visits and &lt; 3 IPTp-SP doses) was highest among the oldest (40–49&#xa0;years) age group with a prevalence of 44.7%, among rural residents (50.4%), women with no formal education (61.6%), and those in the poorest wealth quintile (64.0%) (all <i>p</i> &lt; 0.001). The prevalence of the best-case scenario (4 + ANC visits and 3 + IPTp-SP doses, with at least one dose administered during an ANC visit) was highest among women in the intermediate age group 35–39 (14.1%, <i>p</i> = 0.001). The probability of being in the worst-case scenario was 75% among the poorest women with no education versus 5% among the wealthiest with higher education, indicating significant intersectional inequality, with education having a stronger effect than wealth in reducing missed opportunities.</p> Conclusion <p>The high prevalence and socioeconomic inequality favoring the wealthy and educated of missed opportunities for IPTp-SP among pregnant women in Nigeria, suggesting a significant deficiency in IPTp-SP delivery during ANC, and deserve urgent attention from policymakers. Deliberate policy approaches and programmatic actions targeting the poor and less educated pregnant women may address the observed disparities. Further studies are required to understand the influence of demand and supply-side factors on the prevalence and inequalities of missed opportunities for IPTp-SP among pregnant women in Nigeria.</p>