Wearable technologies represent a novel approach in the prevention of obesity and overweight that encourages users to engage in physical activities aided by technological assistance. This is the first meta-analysis to investigate the effects of wearable technologies as physical activity interventions on weight control. Various electronic databases were searched to select eligible articles, including EBSCO, ScienceDirect, and PubMed, from the first available date to January 9, 2019. All analyses were performed using a random-effects model. Moderator analyses were conducted to investigate differences in the effect size. This meta-analysis of 19 randomized controlled trials indicated that wearable technologies as a physical activity intervention achieved a moderate and significant effect size on body weight and waist circumference and large and significant effect sizes on the body mass index. A subgroup analysis confirmed that wearable technologies were more efficient for weight control in individuals with obesity and chronic diseases. A duration of using wearable technologies for a total of more than or equal to 12 weeks was more effective. Meta-regressions have also revealed that the body weight of individuals who received an additional week of treatment could be reduced by more than 0.37%. Wearable technologies offer innovative platforms of physical activity interventions and an efficient method for weight control.