The importance of improving adolescents’ quality of life is widely known, especially with the proliferation of so-called “diseases of civilization” (e.g., stress, anxiety, depression, tension, panic). According to numerous previous studies, personality is a very important influencer of life satisfaction, and altruistic personality is considered an important and positive personality type. Altruism might, therefore, be an effective way to improve adolescents’ life satisfaction. However, under a market economy, it is difficult to form widespread social customs of altruism. Will helping others also benefit you, representing a win–win situation? Against this background, we conduct the first exploration of the relationship between altruistic personality and life satisfaction. A sample of 428 adolescents completed measures of altruism, life satisfaction, and emotion. The main findings were as follows: (1) adolescents with higher levels of altruism have more positive emotions, fewer negative emotions, and higher life satisfaction; (2) emotions mediated the relationship between altruistic personality traits and life satisfaction; (3) empathy predicted life satisfaction not only directly but also indirectly through positive and negative emotions; (4) social responsibility predicted life satisfaction not only directly but also indirectly through positive emotions; (5) interpersonal trust predicted life satisfaction through negative emotions; (6) sociability predicted life satisfaction through positive emotions. In a word, helping others will benefit yourself as well. These findings are of great practical and theoretical significance for improving adolescents’ quality of life, enriching their personality, and enhancing their positive psychological experience. This study’s results can also contribute to instilling the positive social custom of “one for all, all for one”.