Background: Establishing protected areas is a key approach to protecting nature. However, protected areas are often biased towards remote and less productive lands. It is important to evaluate the impacts protected areas have had, or in other words, what changes in outcomes of interest are attributable to protected areas. Studies that evaluate the impact of protected areas on vegetation - the state and processes that support biodiversity - are scarce and published in a range of disciplines. This systematic review will scope, identify, and synthesize studies that quantitatively measure the impact of protected areas on vegetation extent and condition. The findings will be useful for researchers and policy makers and provide important knowledge for setting post 2020 targets of the Convention on Biological Diversity. This review will also identify research gaps in the current evidence base and provide direction for future research. Methods: This review follows the Collaboration for Environmental Evidence guidelines for evidence synthesis and complies with the ROSES (RepOrting standards for Systematic Evidence Synthesis) reporting framework. We will use a comprehensive search strategy developed through several rounds of scoping review to cover databases; Web of Science, Scopus and CAB Abstracts, 16 organizational websites, google scholar and existing review documents. Our search terms and strategies aim to find impact evaluation studies (both peer-reviewed and grey literature) in English from protected areas globally. The search results will be screened at title, abstract, and then full text by two independent reviewers. A quality appraisal of evidence will be conducted using Joanna Briggs Institute (JBI) risk of bias tool. Review results will be presented in the form of narrative synthesis, as well as in meta-analysis form, where data quality and amount allow.