To examine the association between the cost and quality of diets of grade 5 children in Alberta, Canada. We used survey data of 2731 grade 5 students (10-11 years of age), collected between March and June 2014. This survey included the Harvard Youth Adolescent Food Frequency Questionnaire which captures information on intake of 147 food items. On the basis of these food items, we calculated the diet quality, using the Diet Quality Index-International (DQI) and Canada's Food Guide, and costs by accessing prices from four Canadian grocery retailers. We applied linear regression to determine the association of diet quality with costs. We estimated the cost of a child's diet to be CAD $13.19 per day. For the 12% of children with a low diet quality, these costs were $12.12 and for the 66% of children with moderate and 22% with high diet quality, these costs were $13.27 and $13.51, respectively. For every one-unit increase in DQI, the cost of the diet increased by seven cents per day. Diets that met the recommendations for vegetables and fruit and for meat and alternatives were respectively 53 cents and $1.39 higher relative to diets not meeting these recommendations. Costs for unessential food items constituted $1.39 per day. We observed a gradient whereby diets of better quality are costlier. For low-income households, this may lead to a genuine barrier to healthy eating. Initiatives that target unhealthy unessential foods may create the financial space for households to purchase pricier healthier options. Such initiatives may also alleviate future health care costs.