INTRODUCTION: The need for quantitative criteria to appraise the quality of implementation research has recently been highlighted to improve methodological rigour. The Implementation Science Research development (ImpRes) tool and supplementary guide provide methodological guidance and recommendations on how to design high-quality implementation research. This protocol reports on the development of the Implementation Science Research Project Appraisal Criteria (ImpResPAC) tool, a quantitative appraisal tool, developed based on the structure and content of the ImpRes tool and supplementary guide, to evaluate the conceptual and methodological quality of implementation research. METHODS AND ANALYSIS: This study employs a three-stage sequential mixed-methods design. During stage 1, the research team will map core domains of the ImpRes tool, guidance and recommendations contained in the supplementary guide and within the literature, to ImpResPAC. In stage 2, an international multidisciplinary expert group, recruited through purposive sampling, will inform the refinement of ImpResPAC, including content, scoring system and user instructions. In stage 3, an extensive psychometric evaluation of ImpResPAC, that was created in stage 1 and refined in stage 2, will be conducted. The scaling assumptions (inter-item and item-total correlations), reliability (internal consistency, inter-rater) and validity (construct and convergent validity) will be investigated by applying ImpResPAC to 50 protocols published in Implementation Science. We envisage developing ImpResPAC in this way will provide implementation research stakeholders, primarily grant reviewers and educators, a comprehensive, transparent and fair appraisal of the conceptual and methodological quality of implementation research, increasing the likelihood of funding research that will generate knowledge and contribute to the advancement of the field. ETHICS AND DISSEMINATION: This study will involve human participants. This study has been registered and minimal risk ethical clearance granted by The Research Ethics Office, King's College London (reference number MRA-20/21-20807). Participants will receive written information on the study via email and will provide e-consent if they wish to participate. We will use traditional academic modalities of dissemination (eg, conferences and publications).