Purpose: New ways of teaching have been under consideration over the last decade. Thus, this study aims to examine the effects of an interdisciplinary educational approach integrating physical education and mathematics on light and moderate-vigorous physical activity (PA), sedentary behavior, and learning subtraction. Method: Forty-six first-grade students (M[subscript age] = 76.98 ± 3.74 months) wore an accelerometer for 4 weeks to measure their PA levels. For 3 weeks, one group (n = 23) attended their physical education and mathematic lessons separately according to the traditional curriculum development (i.e., regular classroom lessons), and the other group (n = 23) was taught through an integrated curriculum based on an interdisciplinary approach integrating physical education and mathematics where the curricular time devoted to these subjects was unified. Results: Several "t"-test analyses revealed significant between-group differences in all variables following the curricular interventions. Students from the interdisciplinary group reached higher levels of light PA, t(44) = -10.095, p < 0.001, d = 2.97; moderate-vigorous PA, t(44) = -7.950, p < 0.001, d = 2.35; and spent less time in sedentary behavior, t(44) = 13.549, p < 0.001, d = 4.01, than students who attended regular classroom lessons. Moreover, the students from the interdisciplinary group achieved higher scores in subtraction learning, t(44) = -4.06, p < 0.001, d = 1.20. Discussion/Conclusion: The integration of PA into learning environments such as mathematics might help to develop tools that improve mathematical learnings (i.e., subtraction). Likewise, this kind of interdisciplinary approach may contribute to increase the children's PA levels during the school day.