Context: Requirements engineering in global scaled agile software development and the planning phase for a multi-vocal literature review. Objective: Develop a protocol to specify the plan which will be followed to conduct a multi-vocal literature review study on requirements engineering in global scaled agile software development. Method: Kitchenham and Charters (2007), and Garousi et al. (2019) guidelines were followed to develop a protocol for multi-vocal literature review. Result: A validated protocol to conduct a multi-vocal literature review. Conclusion: The review protocol consist of five phases enumerated as follows: research questions, search strategies, validation of review process, reporting the review, and making changes to the protocol.