Recently, the concept of Physical Literacy (PL) has emerged as a key concept for promoting active behavior and improving health indicators in adolescents. Overweight and obese adolescents have a low level of Physical Activity (PA), low cardiorespiratory capacity, and high Body Fat percentage (%BF). However, the development of PL in the interest of health improvement has never been studied in overweight and obese adolescents. The objective of this study was to evaluate the impact of an intervention developing PL in overweight and obese adolescents in order to increase their (PA) and improve their health. The study was a prospective, single-arm, non-randomized interventional study. The intervention brings together different actions in PA and dietary education in different adolescent living environments. The study took place over a 9-month period with two data collection times (0; +9 months) and measured Body Mass Index (BMI) and BMI z score, %BF and Skeletal Muscle Mass (%SMM), Moderate-to-Vigorous intensity Physical Activity (MVPA) by accelerometry, CRF, as well as PL by the CAPL-2 tool. Thirteen adolescents (age 11.7 (±1.09) years old) improved their PL scores (+8.3 (±9.3) pts; p ≤ 0.01). BMI z score (−0.3 (±0.3), p ≤ 0.01), their %BF (−3.8 (±4.9); p ≤ 0.01), their CRF (+1.5 (±1.7) mL·min·kg−1; p ≤ 0.01), and their MVPA (+4.6 (±13.7) min/day; p = 0.36). Initiating multidimensional interventions to develop PL in overweight and obese adolescents may be a promising prospect to enable an increase in their MVPA and improve their long-term health. Longer-term randomized controlled interventional studies are needed to confirm these findings.