Background: Depressive disorder is a major societal challenge. Despite the availability of clinically and cost-effective treatments including Internet interventions, the number of patients receiving treatment is limited. Evidence-based Internet interventions promise wide availability and high efficiency of treatments. However, these interventions often do not enter routine mental healthcare delivery at a large scale. The MasterMind project aims to provide insight into the factors that promote or hinder the uptake and implementation of evidence-based Internet interventions by mental healthcare practice. Internet-based Cognitive Behaviour Therapy (iCBT) and videoconferencing facilitating collaborative care (ccVC) will be implemented in routine mental healthcare. The services will be offered to 5230 depressed adults in 15 European regions. The current paper describes the evaluation protocol for this large-scale implementation project. Design: Current summative evaluation study follows a naturalistic one-group pretest-posttest design and assesses three distinct stakeholders: patients, mental healthcare professionals, and mental healthcare organisations. The Model for Assessment of Telemedicine applications (MAST) will be employed to structure the implementation and evaluation study. The primary focal points of interest are reach, clinical effect, acceptability, appropriateness, implementation costs, and sustainability of the interventions in practice. Mixed-methods are used to provide an understanding of what (quantitative) the implementation projects have achieved and their meaning to various stakeholders (qualitative). Discussion: The use of Internet interventions in routine practice is limited. MasterMind attempts to bridge the gap between routine practice and effectiveness research by evaluating the implementation of evidence-based Internet interventions for depressive disorders in routine mental healthcare settings in Europe.