Background: Lifestyle is a set of health-promoting behaviors, which empower individuals to maintain and promote their health and prevent illnesses. Poor lifestyle habits in adolescence endanger individuals' health in adulthood. The present study was performed to analyze the relationship between social capital and lifestyle among a group of Iranian adolescents. Methods: This cross-sectional descriptive-analytic study was performed during year 2014. A stratified random sample of 400 tenth-, eleventh-and twelfth-year students was recruited from boys' and girls' high schools located in Birjand, Iran. Data were collected via a demographic questionnaire, the social capital index, and the adherence to a healthy lifestyle questionnaire. The data were entered in the SPSS software (v. 16). Descriptive statistics measures, such as frequency, mean, and standard deviation, were used to describe the data. Moreover, pearson and spearman correlation analyses, one-way analysis of variance, stepwise regression analysis, as well as independent-sample t, Mann-Whitney U, and Kruskal-Wallis tests were performed for data analysis. Results: Most participants had good social capital and a moderately healthy lifestyle. Social capital was positively correlated with lifestyle (r = 0.49; P < 0.001). Stepwise regression analysis showed that gender and social capital explained 33% of the total variance of lifestyle (R 2 = 0.33; F = 100.52; and P < 0.001).