Exclusive breastfeeding (EBF) for the first six months of life remains one of the most effective interventions for reducing infant morbidity and mortality, yet practice rates in Nigeria continue to fall below recommended targets. Knowledge of breastfeeding and maternal educational attainment are frequently cited as key determinants of EBF uptake, but their combined influence among postnatal mothers in tertiary hospital settings in Rivers State has not been sufficiently explored. This study examined the influence of knowledge and maternal education on exclusive breastfeeding practice among postnatal mothers attending the University of Port Harcourt Teaching Hospital (UPTH) and the Rivers State University Teaching Hospital (RSUTH). A cross-sectional descriptive design was adopted, and data were collected from 279 postnatal mothers using a structured, interviewer-administered questionnaire with a four-point Likert scale. Descriptive statistics (means, standard deviations, frequencies) and Pearson Product Moment Correlation (PPMC) were used to analyse the data. Results showed that respondents strongly agreed that knowledge of EBF influenced their confidence and adherence to recommended practices (grand mean = 3.23), and even more strongly agreed that maternal education shaped their breastfeeding decisions and behaviour (grand mean = 3.25). Correlation analysis revealed a strong, statistically significant positive relationship between knowledge and EBF practice (r = .791, p = .001) and between maternal education and EBF practice (r = .794, p = .002), leading to rejection of both null hypotheses. The study concludes that knowledge and maternal education are significant determinants of exclusive breastfeeding practice among postnatal mothers in tertiary hospital settings. It recommends that structured breastfeeding education be strengthened within antenatal and postnatal care services, and that efforts to address educational disparities among mothers be prioritised to improve EBF rates in Rivers State and similar settings across Nigeria.