BackgroundThere are no nationally representative population-based studies investigating the relationship between physical activity, chronic conditions and multimorbidity (i.e., two or more chronic conditions) in low- and middle-income countries (LMICs), and studies on a multi-national level are lacking. This is an important research gap, given the rapid increase in the prevalence of chronic diseases associated with lifestyle changes in these countries. This cross-sectional study aimed to assess the association between chronic conditions, multimorbidity and low physical activity (PA) among community-dwelling adults in 46 LMICs, and explore the mediators of these relationships.MethodsWorld Health Survey data included 228,024 adults aged ≥18 years from 46 LMICs. PA was assessed by the International Physical Activity Questionnaire (IPAQ). Nine chronic physical conditions (chronic back pain, angina, arthritis, asthma, diabetes, hearing problems, tuberculosis, visual impairment and edentulism) were assessed. Multivariable logistic regression and mediation analyses were used to assess the association between chronic conditions or multimorbidity and low PA.ResultsOverall, in the multivariable analysis, arthritis (OR = 1.12), asthma (1.19), diabetes (OR = 1.33), edentulism (OR = 1.46), hearing problems (OR = 1.90), tuberculosis (OR = 1.24), visual impairment (OR = 2.29), multimorbidity (OR = 1.31; 95% CI = 1.21–1.42) were significantly associated with low PA. More significant associations were observed in individuals aged ≥50 years. In older adults, depression mediated between 5.1% (visual impairment) to 23.5% (angina) of the association between a chronic condition and low PA. Mobility difficulties explained more than 25% of the association for seven of the eight chronic conditions. Pain was a strong mediator for angina (65.9%) and arthritis (64.9%), while sleep problems mediated up to 43.7% (angina) of the association.ConclusionsIn LMICs, those with chronic conditions and multimorbidity are significantly less physically active (especially older adults). Research on the efficacy and effectiveness of PA in the management of chronic diseases in LMICs is urgently needed. Targeted promotion of physical activity to populations in LMICs experiencing chronic conditions may ameliorate associated depression, mobility difficulties and pain that are themselves important barriers for initiating or adopting an active lifestyle.Electronic supplementary materialThe online version of this article (doi:10.1186/s12966-017-0463-5) contains supplementary material, which is available to authorized users.