Background: The first five years of a child’s life is a golden period for their growth and development, fostering their future learning skills and social and emotional abilities due to rapid gains in physical and cognitive growth and development. Objectives: The aim of this study was to examine the knowledge of mothers about the growth and development of under 5-years children in western Rajasthan. Materials and Methods: The present study was conducted with quantitative descriptive approach. The study was conducted at Prince Bijay Singh Memorial (PBM) Hospital, Bikaner, Rajasthan. The population of the current study comprised of 150 mothers, having at least an under-5 year’s child. The subjects were selected by Non-probability convenient sampling technique for this study. Self-structured questionnaire on demographic profile and knowledge about growth and development were distributed among the mothers. Results: The study revealed that half of the mothers were belongs to 26–35 years of age group. The majority of mothers (42%) were having education up to primary level. In occupational status, the most of mothers (56.66%) were house wife. Furthermore, the majority of the mothers (65.33%) had average level of knowledge followed by 28.67% of them had good level of knowledge while only 6% had poor level of knowledge regarding growth and development of under-5 year children. Likewise there was a significant association between the knowledge scores of the mothers and age (p-value- 0.031), educational status (p-value- 0.0001) and occupation (p-value- 0.0001). Whereas, variables like as: family income, type of family and Number of children in family were not significantly associated the level of knowledge. Conclusion: Findings of this research study suggested that most of the mothers having average level of knowledge towards growth and development of under-5 year children. In addition, Knowledge of the mothers was partially associated with their selected demographic variables. Furthermore, sound knowledge of mothers is vital for growth and development of under-5 year children.