The objective of this study was to assess whether the standard therapy of ready-to-use therapeutic food in the treatment of uncomplicated severe acute malnutrition (SAM) is effective in improving developmental potential and weight gain in children aged under five years. A multicenter pretest-posttest study was conducted among 91 children aged under five with uncomplicated SAM in Pakistan. Study participants completed their eight weeks’ therapy of ready-to-use therapeutic food according to the World Health Organization’s (WHO) standard guidelines. The study outcome was the proportion of children with improved developmental potential in all domains in comparison with the pretreatment status and children gaining >15% of their baseline weight; mean weight-for-height/length z-score after completing eight weeks’ therapy of ready-to-use therapeutic food. The Denver Development Screening Tool II was used for developmental screening. Significant changes (p < 0.05) were observed for developmental status milestones in terms of gross motor, fine motor, and personal/social milestones, as well as language and global development milestones. There was a strong positive correlation (r = 0.961) between initial weight and weight at the last visit (p < 0.001). Ready-to-use therapeutic food is effective in improving development potential as well as promoting weight gain in children aged under five with uncomplicated SAM if provided according to WHO guidelines.