Background:Childhood under-nutrition is prevalent in many developing countries including Nigeria, and is an underlying cause for more than half of all childhood deaths. Based on the recent Nigeria Demographic and Health Survey (NDHS), the prevalence of under-nutrition between 2008 and 2013 has risen, despite an increase in exclusive breastfeeding (EBF) rate over the same period. This study was carried out to assess the effect of infant and young child feeding practices on , nutritional status of children 0 -24 months in Port Harcourt, Nigeria. Subjects and Methods: Data were collected between November and December 2016 from 307 mother-child (aged 0 -24 months) pairs attending six health centres in Port Harcourt using a pretested self-administered questionnaire. Data collected included maternal and child sociodemographics, mother's infant feeding practices, 24-hour dietary recall and anthropometric measurements. Data were analysed using SPSS version 20.0. Tobi et al.; AJMAH, 17(4): 1-21, 2019; Article no.AJMAH.53821 2 Results: The mean age of the children was 5.6±6.1 months, 207 (67.4%) were under 6 months of age and 100 (32.6%) between the ages of 6 to 24 months. Three hundred and three (98.7%) children were breastfed. The rate of exclusive breastfeeding was 51.7% among the children aged 0 -5.9 months. The mean age at which breastfeeding was stopped was 9.3±5.5 months. The average age at which complementary foods were started was 4.4±1.8 months. All the children on complementary feeding met the minimum feeding frequency, but only 43 (33.6%) met the minimum dietary diversity of 4 or more food groups. Overall, 111 (36.2%) children were fed according to WHO recommendation. 10.1% of the children were overweight/obese, 5.5% were wasted, 6.2% were underweight and 8.8% were stunted. Lack of EBF was positively associated with stunting (p = 0.024). Conclusion: Infant and Young Child Feeding practices among mothers in Port Harcourt fall short of the WHO recommendations, resulting in various types of malnutrition among the children. Therefore, more emphasis should be laid on growth monitoring and promotion services and agespecific nutritional counseling to parents and care-givers. Original Research Article