Objectives This study aims to examine the reported prevalence of sufficient physical activity among adults in Arab countries and to determine the use of validated instruments for assessing physical activity. Study design This is a systematic literature review. Methods This review follows recommendations outlined in the Meta-Analysis of Observational Studies in Epidemiology guidelines. The protocol for this study was preregistered with PROSPERO. Cross-sectional, cohort and intervention studies with a minimum of 300 adults aged ¿18 years assessing physical activity using a questionnaire or other self-report measure in the Arabic language were identified from seven electronic databases (MEDLINE, Embase, Cochrane Database of Systematic Reviews, CINAHL, PsycINFO, SPORTDiscu and PubMed). Databases were searched from 1st January 2008 to 17th September 2018. Descriptive analysis was performed using frequency and percentages. The prevalence of physical activity was calculated as the average prevalence for the reported percentages from the studies with similar tools. Results Fifty studies involving 298,242 participants were included in this review. The mean (range) sample size was 5964.8.1 (323¿197,681). Data were collected from participants in 16 of the 22 Arab countries. Great variation exists across the studies in determining whether adults were sufficiently active or not. Twenty studies reported usable data from the Global Physical Activity Questionnaire and the International Physical Activity Questionnaire (moderate & high categories). In these studies, prevalence of physical activity ranged from 34.2 to 96.9%. It was not possible to compare the other studies owing to variation in instruments used to assess physical activity and in the case definition used for `physically active¿. Conclusions This study highlights the need for wider reporting of physical activity and the adoption of valid and reliable instruments to support the development of evidence-informed policy and programmes at both country and regional level. International tools need to be correctly validated, or context-specific tools must be developed to accurately measure physical activity.Objectives This study aims to examine the reported prevalence of sufficient physical activity among adults in Arab countries and to determine the use of validated instruments for assessing physical activity. Study design This is a systematic literature review. Methods This review follows recommendations outlined in the Meta-Analysis of Observational Studies in Epidemiology guidelines. The protocol for this study was preregistered with PROSPERO. Cross-sectional, cohort and intervention studies with a minimum of 300 adults aged ¿18 years assessing physical activity using a questionnaire or other self-report measure in the Arabic language were identified from seven electronic databases (MEDLINE, Embase, Cochrane Database of Systematic Reviews, CINAHL, PsycINFO, SPORTDiscu and PubMed). Databases were searched from 1st January 2008 to 17th September 2018. Descriptive analysis was performed using frequency and percentages. The prevalence of physical activity was calculated as the average prevalence for the reported percentages from the studies with similar tools. Results Fifty studies involving 298,242 participants were included in this review. The mean (range) sample size was 5964.8.1 (323¿197,681). Data were collected from participants in 16 of the 22 Arab countries. Great variation exists across the studies in determining whether adults were sufficiently active or not. Twenty studies reported usable data from the Global Physical Activity Questionnaire and the International Physical Activity Questionnaire (moderate & high categories). In these studies, prevalence of physical activity ranged from 34.2 to 96.9%. It was not possible to compare the other studies owing to variation in instruments used to assess physical activity and in the case definition used for `physically active¿. Conclusions This study highlights the need for wider reporting of physical activity and the adoption of valid and reliable instruments to support the development of evidence-informed policy and programmes at both country and regional level. International tools need to be correctly validated, or context-specific tools must be developed to accurately measure physical activity.