The extensive literature and research on bullying illustrates the connections between self-esteem and the bullying phenomenon, asserting that both faces, bullying, and being bullied are related to some degrees with low self-esteem. Considering the bullying behavior as a form of aggressivity and being bullied as an expression of passive behavior, this study introduces the third subject of inquiry: the assertive behavior. The study investigates the impact of self-esteem on assertiveness, passive vs. aggressive conduct, and positive interactions among high school students. While these aspects were usually investigated at an early age, this study approaches them in adolescence, involving 82 adolescent students from high schools from Timisoara, with diverse specializations. The need to fit, the need for acceptance, and the fear of social rejection increase in adolescence. At this age of dramatic changes, students are susceptible to verbal, physical, or emotional bullying, with an essential impact on their self-esteem, as they are very dependent on peers' approval, perceptions and reactions. Healthy self-esteem and assertiveness might be powerful tools to fight against bullying, but there is very little focus on teaching them in traditional education. This study shows the strong correlation between self-esteem and assertiveness, and the predisposition of students with low self-esteem to passive or aggressive types of interactions.