This study examined the relationship between peer group pressure and responsibility behavior of adolescents. One hundred forty one boys and one hundred fifty girls from three conveniently selected secondary and preparatory schools completed scales pertaining to peer group pressure and responsibility behavior. The study adopted a correlational study design and samples were drawn based on Proportionate Stratified Systematic Random Sampling. Descriptive statistics such as frequency and percentage with tables, mean, median, standard deviations, one sample t â€“test, independent sample t - test, Pearson product-moment correlation, and multiple regression were used to analyze the data. The findings of the study indicate that secondary and preparatory school students are generally low in the three dimensions of responsibilities â€“ related matters and perceive high positive and negative peer group pressures differently. There was also no statistically significant mean difference between males and females in rating of responsibility behavior and peer group pressure. In contrast, there was grade level difference in responsibility behavior and peer group pressure among students. Significant and positive relationship between age and responsibility behavior (i.e. personal, peer, and community) and positive peer group pressure and responsibility behavior (i.e. personal, peer, and community) were found in the study. Whereas, there was negative relationship between negative peer group pressure and dimensions of responsibility behavior (i.e. personal, peer, and community). Finally, positive peer group pressure was the most influential variable in predicting responsibility behavior of students. The study has revealed that students tended to be more responsible with responsibility related matters, when the positive peer group pressure increases as it was related to desirable behaviors. In contrast, students tended to be less responsible with responsibility related matters, when the negative peer group pressure increase as it was related to undesirable behaviors. It was recommended that concerned bodies, i.e. parents and school administrators should understand the influence of peer groups or classmates related to either desirable behaviors or undesirable behaviors which encourage or discourage students to develop responsibility behavior, so that they should devise intervention strategies to make the peer group environment constructive in the way of minimizing the negative aspects of peer group.