Emerging adulthood is a transitional stage between late adolescence and young adulthood in life-span development that requires significant changes in people's lives. Therefore, identifying protective factors for this population is crucial. This study investigated the effects of regular physical activity on self-esteem, optimism, and happiness in emerging adults. Participants included 175 girls (47%) and 198 (53%) boys (M = 20.75 years; SD = 1.69). Participants completed measures of self-esteem, optimism, and happiness. Results suggested that individuals who engage in regular physical activity are more likely to have higher self-esteem, optimism, and happiness than physically inactive emerging adults. Regular physical activity should be regarded as a viable tool for improving subjective well-being in emerging adults.