This study investigates the relation between family climate and mood, social relations and school achievement among adolescents. It also investigates the predictive strength of positive and negative family climate in predicting moods, social relations and school achievement. The study was conducted in two parts over the course of 3 years. The first part was conducted on primary school students in Rijeka between 11 and 14 years of age. The second part was conducted three years later on students between 14 and 17 years of age. Both parts of the study comprised 172 participants in total: 75 boys and 98 girls. In the first part of the study, the participants answered the Family Function questionnaire. In the second part of the study, the participants answered the Positive and negative mood scale and the Social relation questionnaire, and their average school grade results were collected. The aim of this study was to investigate the relation between family climate and mood, social relations and school achievement among adolescents after 3 years. Another aim was to investigate the predictive strength of positive and negative family climate in predicting moods, social relations and school achievement of students after 3 years. Based on the first hypothesis, the prediction of the study is that adolescents in families with positive family climate will have more positive mood, higher quality of social relations and better achievement in school. Based on the second hypothesis, the prediction of the study is that family climate will be positive predictor of mood, social relations and school achievement among adolescents after 3 years. The results of the study show that there is significant and positive relation between family climate with respect to positive moods, social relations with family members and achievement in school. Furthermore, the results show moderately positive relation between family climate and social relations with peers. The results also show that both positive and negative family climate has a significant role in predicting positive moods, social relations with peers, social relations with family members and achievement in school. However, positive family climate is better in predicting positive moods, social relations with family members and school achievement than the negative family climate.