In Ethiopia many women do not practice appropriate complementary feeding (CF). The Health Belief Model (HBM) asserts that change in behavior is determined after consideration of severity, benefit, and barriers to change. This study examined the effectiveness of 3 months of HBM-based education compared to the traditional (didactic) method on CF practices of mothers, with no education as control, using three randomized groups. One hundred sixty-six mother-infant (6–18 months) pairs were recruited. At baseline and after intervention, knowledge, perceptions, and practices about CF and related areas were determined. It was only diet diversity that increased significantly in the HBM group (from 3.05 ± 0.94 food groups to 3.79 ± 0.82, p < .05) while the other two groups had no change. Improvements in food groups were most noticeable as legumes & nuts (from 35.6% use to 83.9% in HBM group). Thus, nutrition education about diet diversity improvement needs to be conducted promotes behavior change. [ABSTRACT FROM PUBLISHER]