Background: Schools can reduce student access to competitive foods and influence healthy food choices by improving the school nutrition environment. This study describes changes in competitive nutrition environments in 100 K-8 schools participating in the Philadelphia Campaign for Healthier Schools. Methods: Interviews with school staff were used to elicit information about policies, practices, and guidelines to restrict/limit competitive foods in schools, before and 1 year into the campaign. To increase the validity of responses, respondents provided documentation for reported policies and guidelines. Baseline interviews were conducted between April and June 2011 and follow-up interviews were conducted between April and June 2012. Results: At follow-up, significantly more schools reported having policies and/or guidelines in place to regulate food as a reward in the classroom, food served at parties and celebrations, outside foods allowed in school, and the availability of sodas and sugar-sweetened beverages. There were no measurable effects on food available in school stores, fundraisers, or afterschool programs. Availability of concrete documentation of policies was limited, but when provided, it corroborated the interview responses. Conclusions: In the context of a comprehensive school wellness policy, school wellness councils were associated with increases in school-level policies and practices that improved the competitive nutrition environment.