The infant is a dynamic, ever-changing being who undergoes an orderly and predictable sequence of neuro developmental and physical growth. This sequence is influenced continuously by intrinsic and extrinsic forces that produce individual variation and make each infant’s developmental path unique. Parents need to understand growth and development in order to monitor child’s progress, to identify delays or abnormalities in development. By monitoring child and family the nurse can observe the inter-relationship of physical growth and cognitive, motor and emotional development. Therefore a descriptive study to assess the knowledge of mothers regarding developmental milestones of infants in selected hospital of Ludhiana Punjab was undertaken with the objectives: to assess the knowledge of mothers regarding developmental milestones of infant and to ascertain the relationship of knowledge of mothers with selected demographic variables. A non-experimental, descriptive study was conducted in various child care areas of selected hospital Ludhiana, Punjab. The study sample consisted of total 100 mothers of infants from child care areas. Data was analyzed by inferential statistics and presented through tables and figures. Findings revealed that maximum number of mothers (53%) had good knowledge score regarding developmental milestones of infants. Mean percentage and rank order of knowledge score was highest in introduction (63% and rank 1st) and lowest in the area of social development (21% and rank 6th). Variables i.e. age, parity, educational status, occupation, monthly family income, source of information, place of living and number of children were found to be non significant.