Data on the association between informal caregiving and physical activity (PA) levels are scarce, especially from low- and middle-income countries (LMICs). Furthermore, previous research has yielded conflicting results. Thus, we investigated this association in adults from 38 LMICs. Data from the World Health Survey (WHS), a cross-sectional, predominantly nationally representative survey conducted in 2002–2004, were analyzed. PA was assessed by the International Physical Activity Questionnaire and participants were dichotomized into those who do (≥150 min of moderate-to-vigorous PA per week) and do not (<150 min = low PA) comply with the World Health Organization PA recommendations. Those who provided help to a relative or friend (adult or child), because this person has a long-term physical or mental illness or disability, or is getting old and weak in the past year were considered to be informal caregivers. Multivariable logistic regression analysis was conducted to assess the associations. There were 204,315 adults aged ≥18 years from 38 LMICs included in this study [mean (standard deviation) age 38.6 (16.1) years; 50.7% female]. Overall, the prevalence of caregiving and low PA was 19.5% and 29.9%, respectively. After adjustment for potential confounders, caregivers were at a lower risk for low PA compared to non-caregivers (OR = 0.79; 95% CI = 0.72–0.86). Engagement in greater number of caregiving activities was associated with lower odds for low PA dose-dependently. Informal caregiving was associated with higher levels of PA in adults in LMICs. Future studies of longitudinal design are warranted to understand causality and the underlying mechanisms of this association.