Food availability and access are strongly affected by seasonality in rural households in Ethiopia. However, relationships between household food insecurity indicators and dietary diversity and nutritional status of reproductive age mothers and their young children are unclear. A longitudinal study was conducted among 800 farming households in lowland and midland agro-ecological zones of rural Ethiopia in pre and post-harvest seasons. A structured interview, which included measures of three food access indicators - household food insecurity access scale (HFIAS), household dietary diversity score (HDDS) and household food consumption score (HFCS)¿-¿was conducted. Additionally, a subset of 183 households was selected for assessment of indicators of nutritional status including maternal and child dietary diversity and anthropometric measurements for children 6–23 months of age. Magnitudes of household food insecurity indices were high by international standards, particularly during the lean season (pre-harvest). Using correlation, Chi square and multivariable regression models, HFCS in both seasons was related to maternal body mass index and haemoglobin, and weight-for-length of their children. HDDS was associated in the post-harvest season with haemoglobin level of the mothers, and weight-for-length of their children. HFCS was a better predictor of nutritional status of mothers and children in both the food surplus and lean seasons, while HDDS was a better predictor of maternal and child nutritional status post-harvest. It is recommended that nutritional interventions should therefore focus on household food insecurity as well as targeting the individual nutritional status of mothers and children.