This study aims to investigate whether the socio-emotional contextualization of envy influences the interpretation of and reaction to hostile messages on WhatsApp among Spanish adolescents. A total of 190 high school students participated. Participants read two stories containing a hostile message. In one condition, the hostile message preceded by a situation of envy, in the other it was not. We asked participants to attribute emotions and rate whether the message was offensive or funny, the intention of the message, and the relative status of the characters. The results showed that participants identified shame and sadness in the victim, but girls were better than boys at identifying envy in the aggressor. In addition, more girls disapproved of the hostile message than boys in the envy condition. On the other hand, girls perceived the hostile message as more offensive and understood it as teasing, whereas boys interpreted it as funnier and understood it as a joke. Finally, participants understood that the aggressor felt more inferior to his victim in the envy situation than in the non-envy situation. The discussion addresses the implications of these findings for the socio-emotional contextualization of cyber aggression and highlights the importance of evaluating hostile messages, presumably more prevalent during adolescence than other types of cyber aggression.