Background: Micronutrient deficiency is one of the major problems commonly seen in children below 5 years of age. Aim: to determine the effect of a coaching program on mothers' knowledge regarding micronutrients and their children's development under five years. Design: a quasi-experimental design (pre/post-test).  Setting: The study was conducted at Pediatric Outpatient Clinic at Sohag University Hospital and Dar El Salama Abdallah Maternal and child health center in Sohag City. Subjects: convenience sampling technique consisted of 100 mothers and their children from the above-mentioned setting recruited in this study. Tools: Three tools were used for data collection: Tool I: Structured interview questionnaire; Tool II: Bayley Scales of Infant and Toddler Development; Tool III: Brief Infant Toddler Socio-Emotional Assessment sheet, Tool IV: Children blood test assessment sheet.  Results: The study result revealed that (80%) of mothers possessed unsatisfactory knowledge levels regarding micronutrients. The analysis showed that there is no association between the level of knowledge of mothers regarding micronutrients with their selected demographic variables. Pre coaching program there were no statistically significant differences between mothers related to their level of knowledge about micronutrients (p > 0.05). While there were significant differences in post-knowledge scores regarding micronutrients pre and post-coaching program (p< 0.001). There was a significant improvement in children's socioemotional development. Conclusion: A coaching program regarding micronutrients had a positive effect on mothers' knowledge regarding micronutrients and their children's development under five years. Recommendations: Continuous application of the coaching program for mothers of children under five years to improve their knowledge regarding micronutrients which reflected positively on their children's development.