The World Health Organization's (WHO) standardized questionnaire for assessing infant and young child feeding practices does not include commercial baby cereals (CBC), which are derived from several food groups and are fortified with micronutrients. We examined how different scenarios for classifying CBC affect estimates of the quality of complementary feeding in children ages 6−23 months in Vietnam in 2014 (n = 4811). In addition to the WHO standardized 24-h recall questionnaire for infant and young child feeding, we asked mothers about the consumption of CBC. The five resulting scenarios were S1 – omitted CBC; S2 – CBC classified as grains; S3 – as grains and dairy; S4 – as grains, dairy and fruit/vegetables; and S5 – as grains, dairy, fruit/vegetables and any others. Including CBC resulted in 4−11 percentage points higher in the prevalence of children who were fed each of the six food groups compared with what was reported in the WHO standardized questionnaire. Minimum dietary diversity (% fed ≥ 4 out of the 7 food groups) was higher in S5 (90%) than in S1 (84%), S2 (84%), S3 (85%) and S4 (86%). Minimum acceptable diet was also higher in scenarios S5 (80%) than in S1 (74%), S2 (75%), S3 (75%) and S4 (77%). Consumption of iron-rich foods was 94% when CBC was accounted, which was higher than the alternative scenario (89%). In summary, when CBC were included, population-level estimates of dietary quality were higher than when CBC were omitted. Guidance is required from the WHO about how to account for the consumption of CBC when estimating the quality of complementary feeding.