This paper is based on a report commissioned by the United Nations High Commissioner for Refugees, which aims to provide information on cultural aspects of mental health and psychosocial wellbeing relevant to care and support for Syrians affected by the crisis. This paper aims to inform mental health and psychosocial support (MHPSS) staff of the mental health and psychosocial wellbeing issues facing Syrians who are internally displaced and Syrian refugees. We conducted a systematic literature search designed to capture clinical, social science and general literature examining the mental health of the Syrian population. The main medical, psychological and social sciences databases (e.g. Medline, PubMed, PsycInfo) were searched (until July 2015) in Arabic, English and French language sources. This search was supplemented with web-based searches in Arabic, English and French media, and in assessment reports and evaluations, by nongovernmental organisations, intergovernmental organisations and agencies of the United Nations. This search strategy should not be taken as a comprehensive review of all issues related to MHPSS of Syrians as some unpublished reports and evaluations were not reviewed. Conflict affected Syrians may experience a wide range of mental health problems including (1) exacerbations of pre-existing mental disorders; (2) new problems caused by conflict related violence, displacement and multiple losses; as well as (3) issues related to adaptation to the post-emergency context, for example living conditions in the countries of refuge. Some populations are particularly vulnerable such as men and women survivors of sexual or gender based violence, children who have experienced violence and exploitation and Syrians who are lesbian, gay, bisexual, transgender or intersex. Several factors influence access to MHPSS services including language barriers, stigma associated with seeking mental health care and the power dynamics of the helping relationship. Trust and collaboration can be maximised by ensuring a culturally safe environment, respectful of diversity and based on mutual respect, in which the perspectives of clients and their families can be carefully explored. Sociocultural knowledge and cultural competency can improve the design and delivery of interventions to promote mental health and psychosocial wellbeing of Syrians affected by armed conflict and displacement, both within Syria and in countries hosting refugees from Syria.