Contaminated drinking water and unhygienic methods for disposal of waste or sanitation for a large proportion of population are common realities in developing countries. The impact of sources of pollution on different dimensions of well-being of human race have been extensively investigated as it can largely affect physical health and cognitive abilities of preschool children. Impact of unclean water and poor sanitation on child undernourishment is not clearly investigated in Pakistan, although this link is one of the most prominent cause of children fatalities globally. This thesis studies the impact of the drinking water quality and sanitation service on the probability of being malnourished among children in Pakistan. This study specifically accesses the association of malnutrition with social and economic factors, in general, and environmental factors, in specific, such as sanitation facilities and drinking water sources for Pakistan. Moreover, this research examines the determinants of male and female child malnutrition in Pakistan while, in specific, the role of the sanitation facility and drinking water source in gender analysis. The study used a sample of 1,004 under-three children extracted from the data of Pakistan Demographic and Health Surveys 2017-18. Composite Index of Anthropometric Failure (CIAF) was generated to measure malnutrition among children based on height for age Z score (HAZ), weight for age Z score (WAZ), and weight for height Z score (WHZ). In the study we used binary logistic regression to analyze the probability of malnourishment among children. The results of the study depict that the mothers with five years of schooling and 10 years of schooling, had 65.5% [primary (CI: 0.42-1.04] and 40% [high (CI: 0.23-0.72)] lower chances of malnutrition prevalence among their children. Household belongs to richer and richest quantile, had 57.9% [richer (CI: 0.34-0.99)] and 40.3% [richer (CI: 0.22-0.74)] lower probability of undernutrition prevalence among their children. The results further portray that households who have improved water source, had 71.5% (95% of Confidence Interval: 0.51-1.01) lower chances of undernutrition prevalence among their children. Same as, the households who have improved toilet or sanitation facility, had 68.9% (95% CI: 0.52-0.91) less chances to experience the occurrence of malnutrition among their children. The binary logistic regression results for gender-disaggregated analysis show that households who have improved water sources had 62.1% (95% Confidence Intervals: 0.37-1.03) lower probability to experience the undernutrition among their male children. Sanitation variable was insignificant in male model. Similarly, households who have improved sanitation facility had 64.1% (95% Confidence Intervals: 0.43-0.95) lower chances of undernutrition prevalence among their female children. Water variable was insignificant in female child model. This study concludes that human development projects like education to every child Ahsaas Program etc. should be expended more for human development along with the plans to advance water and sanitation facility should be entered into the priority lists to not only save human from water and sanitation borne diseases but also could reduce child malnutrition as well as it also uplifts the standard of living of common folk. Supervision:- Dr. Hafsa Hina