Technical Abstract: Nutritionally at-risk children suffer delays in physical growth and motor and language development. Infectious diseases such as malaria pose an additional risk. We examined the cross-sectional relationships among malaria infection, hemoglobin (Hb) concentration, length-for-age Z-scores (LAZ), motor activity, behavior, and motor and language development in 841 Zanzibari children 5–19 mo old. We used structural equation modeling to test the fit of the data to a theoretical model and to examine the relationships among the variables in 3 age groups (5–9, 10–14, and 15–19 mo). The model fit the data for all age groups. In the youngest and oldest groups, children with higher malaria parasite densities had significantly lower Hb and LAZ. Higher LAZ significantly predicted higher total motor activity, and motor and language development scores in all age groups. In the oldest group, children who had higher Hb had higher motor development and activity scores. Malaria was directly and indirectly related to motor activity in the 10- to 14-mo-old group [standardized total effects, 20.14; direct, 20.10 (P = 0.015); and indirect, 20.038]. The significant fit of the models to the data and the statistical significance of many of the specific pathways highlight the complexities of the relationships between health and nutrition and child development outcomes in this population. In addition, the results suggest that multiple interventions are likely necessary to improve child development outcomes in this population of nutritionally at-risk children and that the potential effectiveness of interventions may differ according to age (i.e. prevention and treatment of anemia, stunting, and malaria).