Family meals have been associated with higher diet quality and reduced risk of obesity in children. Observational studies of the family meal have been employed with increasing frequency, yet there is currently no tool available for measuring the healthfulness of food served during the meal. Here we present the development and validation of the Healthy Meal Index (HMI), a novel tool for scoring the healthfulness of foods served to children during a meal, as well as sociodemographic predictors of meal scores. Parents of 233 children, aged 4–8 years, self-recorded three home dinners. A research assistant obtained a list of foods available during the meal (meal report) via phone call on the night of each video-recorded meal. This meal report was coded into component food groups. Subsequently, meals were scored based on the availability of more healthy “Adequacy foods” and the absence of “Moderation foods”, (of which reduced consumption is recommended, according to pediatric dietary guidelines). Adjusted linear regression tested the association of sociodemographic characteristics with HMI scores. A validation study was conducted in a separate sample of 133 children with detailed meal data. In adjusted models, female children had higher HMI Moderation scores (p = 0.02), but did not differ in HMI Adequacy or Total scores. Parents with more education served meals with higher HMI Adequacy (p = 0.001) and Total scores (p = 0.001), though no significant difference was seen in HMI Moderation score (p = 0.21). The validation study demonstrated that the HMI was highly correlated with servings of foods and nutrients estimated from observations conducted by research staff. The HMI is a valuable tool for measuring the quality of meals served to children.