The Netherlands Nutrition Centre has developed ‘Guidelines for Healthier Canteens’. To facilitate their implementation, implementation tools were developed: stakeholders’ questionnaires, the ‘Canteen Scan’ (an online tool to assess product availability/accessibility), a tailored advisory meeting/report, communication materials, establishment of an online community, newsletters, and a fact sheet with students’ wishes/needs. In this quasi-experimental study, we investigated the effect of these tools in secondary schools on (a) factors perceived by stakeholders as affecting implementation; (b) the quality of implementation. For six months, ten intervention schools implemented the guidelines, supported by the developed implementation tools. Ten control schools received the guidelines without support. School managers, caterers, and canteen employees ( n = 33) reported on individual and environmental factors affecting implementation. Implementation quality was determined by dose delivered, dose received, and satisfaction. Stakeholders ( n = 24) in intervention schools scored higher on the determinants’ knowledge and motivation and lower on need for support ( p < 0.05). Dose received (received and read) and satisfaction was highest for the advisory meeting/report (67.9%, 64.3%, 4.17), communication materials (60.7%, 50.0%, 3.98), and fact sheet (80%, 60%, 4.31). Qualitative analyses confirmed these quantitative results. In conclusion, a combination of implementation tools that includes students’ wishes, tailored information/feedback, reminders and examples of healthier products/accessibility supports stakeholders in creating a healthier school canteen.