This study examined the effectiveness of a physical activity (PA) intervention among obese Hispanic children delivered by a free mobile phone game application (app) recommended by a pediatrician. A sample of 40 (age M=10.16[2.01] years) children participated in this pilot study. Pre- and posttest data were collected on participants' PA attitudes, intention, and objectively measured PA. The intervention was a game-based exercise prescription to engage in at least 20 minutes daily for seven days in moderate-to-vigorous PA (MVPA) delivered by their primary care pediatrician. The results showed a statistically significant decrease in sedentary time (SED) (t(26)=3.03, p=0.007, d=0.66) and an increase in moderate PA (MPA) (t(26)=3.19, p=0.005, d=-0.69), vigorous PA (VPA) (t(26)=-5.74, p<0.001, d=-1.25), and MVPA (t(26)=-9.09, p<0.001, d=-1.89). In addition, the study showed increase in PA attitudes (t(26)=-3.63, p<0.001, d=-1.10) and PA intention (t(20)=-3.13, p=0.001, d=-0.94) after the intervention. This study provides evidence that a mobile app gaming-based exercise prescription may help to engage obese Hispanic children in health enhancing PA.