Introduction. Mass deworming of preschool children is a strategy suggested to prevent soil-transmitted helminth infections in most developing countries. Nonetheless, there is a scarcity of data showing the contribution of mass deworming to a child’s nutritional status. The purpose of this study was to assess the effect of deworming on nutritional health outcomes (stunting, underweight, and anemia) in children aged 12 to 59 months. Methods. A secondary analysis of data extracted from the Tanzania Demographic and Health Survey (TDHS) 2015-16 data was carried out. A total of 7,962 children were included in this study. A multilevel logistic regression was used at a 5% level of significance to determine the individual- and community-level determinants of deworming on health outcomes among children. Results. The prevalence of underweight (62.6%), stunting (61.0%), and anemia (61.8%) was higher in children who were not dewormed than those who were dewormed. Female children were more likely to suffer from poor health outcomes (OR = 1.01 and 95% CI = 0.95–1.07) than male children. Children aged 24–35 months and 36–47 months were significantly less likely to suffer from poor health outcomes (OR = 0.89; 95% CI = 0.82–0.97 and OR = 0.88; 96% CI = 0.81–0.96, respectively;
p
<
0.01
). Children from households with unimproved toilets (OR = 1.38 and 95% CI = 1.25–1.52), unimproved water sources (OR = 1.08 and 95% CI = 1.01–1.16), and living in rural areas (OR = 1.02 and 95% CI = 0.91–1.14) had higher odds for poor health outcomes. Conclusion. Deworming may be an effective technique for preventing poor health outcomes in children and the risks associated with them, such as poor growth and development.