This study was conducted to evaluate seasonal patterns of household food insecurity, dietary diversity, and household characteristics on wasting and stunting among children in households followed for 1 year in the drought-prone areas of Sidama, Ethiopia. A cohort study design was employed. Data were collected on the pre-harvest season (March and June) and post-harvest season (September and December) of 2017. We studied 935 children aged 6 to 47 months. At four seasons over a year, we had 3,449 observations from 897 households and 82% (2,816) (95% CI: 80.3-82.9) were food in-secured households. Severe food insecurity was higher in the pre-harvest (March; food scarcity season) which was 69% as compared to 50% of September (P < .001). From 3,488 observations, 44% (1,533) (95% CI: 42.3-45.6) of children were stunted. Stunting showed seasonal variations with 38% (95% CI: 34.7-41.0) in March and 49% (95% CI: 45.8-52.5) in December. Six percent (95% CI: 5.0-6.6) of children were wasted, with higher prevalence in March (8%) as compared to 3% of September (P < .001). Moreover, household characteristics such as poverty level, education, occupation and the household food insecurity and dietary diversity were associated with subsequent wasting and stunting.