Background: Knowledge and practices of postnatal mothers is very crucial in providing care to newborns. Aim was to assess determinants of the knowledge and practices of postnatal mothers on essential newborn care.Methods: A community based cross-sectional study was conducted among 150 postnatal mother - neonate dyads in one of the selected Primary Health Centres (PHC) of rural Haryana. A self-developed, pre-tested and validated structured interview schedule containing socio-demographic, clinical profile information and a knowledge and practice questionnaires (α-0.79, 0.86) having 38 multiple choice questions (MCQs) and 28 items respectively were used for data collection covering various aspects of essential newborn care such as thermal care, breastfeeding, cord care, eye care, handwashing, and danger signs. Results: More than half (52%) of the postnatal mothers had moderate knowledge and 76.7% of postnatal mothers reported of adequate practices. Gaps were identified in terms of knowledge and practices in the domains of thermal control, breastfeeding, cord care and eye care. Overall knowledge and practice scores of postnatal mothers were positively correlated (r =0.71, p<0.001). Significant association was observed between the overall practice scores and socio-demographic variables of postnatal mothers such as religion [AOR] (4.96 95%CI; 1.21-20.2), level of education (47.5 95%CI; 2.8-820.2), socio-economic status (16.9 95%CI; 0.9-288.4).Conclusions: Some gaps were observed in the adopting safe practices in the domains of thermal control, breastfeeding, cord care and eye care among the postnatal mothers; necessitating need for education, reinforcement and dispelling the cultural beliefs.