Regular physical activity (PA) improves mental health and reduces the risk of a number of adverse health outcomes, including cardiovascular disease mortality, hypertension, colon cancer, and diabetes mellitus. Many studies with different strategies have been conducted to increase the level of PA for people of all ages. One of many strategies applied in intervention studies is the use of pedometers as a motivational tool. Pedometers are simple and inexpensive body-worn motion sensors that researchers and practitioners use to assess and motivate PA behaviors. Most of the pedometer-based intervention studies report an increase in PA by the intervention group, but the magnitude of this increase and the effect of other variables (e.g., age and sex of participants, intervention length) are not known. A meta-analysis of those intervention studies can provide more information about the magnitude of change and the effect of those variables. Thus, the purpose of this study was twofold. The first goal of this study was to use meta-analysis to determine the magnitude and direction of effects in pedometer-based interventions. The results showed that the use of pedometers has a moderate and positive effect on the increase of PA in intervention studies. The second goal was to determine if age and sex of participants, intervention length, and intervention strategy influence the effectiveness of the intervention. The cumulative evidence suggested that all the moderators influence the effect of pedometer-based PA interventions. (Contains 2 tables and 1 figure.)