ABSTRACT
INTRODUCTION: Youth mental health is a global issue, with 75% of many serious mental health difficulties emerging before the age of 25. An increase in the popularity of online counselling for young people's mental health has been seen in recent years, due to their accessibility, cost-effectiveness and reduced stigmatising effects. Online synchronous chat counselling consists of real-time, text-based, one-to-one chats with a mental health professional and/or trained volunteer. Literature to date examining the effectiveness of these interventions has been limited, and little is known about their design features, their acceptance, effectiveness and the therapeutic processes that contribute to their working. METHODS AND ANALYSIS: A mixed-methods systematic review of the literature will be conducted. PsycINFO MEDLINE, CINAHL, Web of Science and relevant grey literature will be searched for peer-reviewed, English language studies between January 1995 and June 2021. Backward and forward reference checking will be conducted. Quality of included articles will be examined using the Mixed Methods Appraisal Tool and a combination of the TIDieR checklist and a prepopulated data table will be used for extraction. A mixed methods review adopting a convergent-integrated design will be employed. Quantitative data will be transformed and analysed simultaneously alongside qualitative data using narrative synthesis. ETHICS AND DISSEMINATION: The research does not require ethical approval. Findings will be disseminated through peer-reviewed publications, academic conference presentations, academic social media and invited workshops, webinars and seminars. PROSPERO REGISTRATION NUMBER: CRD42021256016.