Adolescence is a critical stage of human development, marked by profound biological, psychological, and social changes. Regular physical activity during this period plays a vital role in promoting physical and mental health, enhancing cardiorespiratory fitness, musculoskeletal development, healthy weight regulation, psychological well-being, and social integration. Despite these well-documented benefits, physical activity levels among adolescents remain worryingly low, with only 27–33% meeting the World Health Organization recommendation of at least 60 min of moderate-to-vigorous intensity physical activity per day. Exercise prescription for adolescents must be thoughtfully designed and based on the FITT-VP (frequency, intensity, time, type, volume, and progression) principles while being adapted to the individual’s biological maturation, physical fitness level, and psychosocial context. It is essential to recognize the so-called “windows of opportunity,” sensitive periods during which the adolescent body is more responsive to specific training stimuli. To maximize engagement and enjoyment, physical activity should be varied, developmentally appropriate, and socially meaningful. School settings, sports clubs, and informal peer-based activities represent key environments for promoting sustained participation. Motivational strategies such as setting clear goals, fostering perceived competence, and encouraging family and school support play a decisive role in building long-term active habits. Exercise prescription during adolescence should be guided by qualified professionals who can ensure that interventions are not only safe and effective but also enjoyable and tailored to individual needs. These programs support the formation of healthier and more active lifestyles that can continue throughout life.