Pregnancy is a major life event that brings emotional and physical changes while increasing nutritional demands. Proper nutrition during pregnancy is essential for maternal health and fetal development, reducing risks such as low birth weight and maternal anaemia. However, many pregnant women in Nigeria face challenges, including socio-cultural beliefs, limited nutritional knowledge, and economic constraints, leading to malnutrition and poor outcomes. This study investigates the knowledge, attitudes, and practices (KAP) regarding maternal nutrition among expectant mothers in Warri, Delta State, Nigeria. A facility-based cross-sectional study was conducted with 341 pregnant women selected through random sampling. Participants were aged 18–49 years and had lived in Warri for over six months. Data collection involved an adapted questionnaire, and analysis was performed using SPSS version 25. Statistical significance was set at p < 0.05. The mean age of participants was 32.39 years (±7.864). Results showed that 56% had poor knowledge, 53% demonstrated poor attitudes, and 62% exhibited inadequate practices. Educational attainment significantly influenced attitudes, with primary education associated with reduced odds of positive attitudes (COR: 0.231, AOR: 0.216). Similarly, the number of pregnancies significantly impacted nutritional practices (COR: 0.447, AOR: 0.415). Among the reasons cited by expectant mothers for prohibiting certain foods during pregnancy, two key factors emerge cultural beliefs (42.1%) and lack of knowledge (42.4%). This highlights the influence of traditional practices and informational gaps in shaping dietary behaviours. These restrictions can significantly affect maternal health, potentially limiting access to essential nutrients needed for fetal development and maternal well-being. Significant gaps in knowledge, attitudes, and practices highlight the need for targeted nutrition education and culturally sensitive support programs to improve maternal dietary behaviour. Health facilities should also enhance antenatal counseling to correct food-related misconceptions, while community and religious leaders can help share accurate maternal nutrition information which will promote better pregnancy outcomes and reducing health risks for mothers and babies