Non-suicidal self-injury or NSSI has been a widespread phenomenon happening in adolescents and is significantly found to be an after-effect of improper emotion regulation due to difficulty in expressing emotions. This study utilized a descriptive-correlational study and was conducted on 126 adolescents to ascertain the correlation between NSSI and emotion regulation and NSSI as an aftereffect of emotion regulation among adolescents. In measuring the levels of NSSI, the researcher used the Functional Assessment of Self-Mutilation (FASM) and Emotion Regulation Questionnaire (ERQ) for emotion regulation. Results of the study reported low levels of NSSI symptoms with computed mean of 0.65 and SD= 0.51 which includes a mild form of NSSI such as biting oneself and pulling out hair and a moderate/severe form which is hitting oneself on purpose. Moreover, the study revealed high levels of emotion regulation among the respondents with mean=4.71 and SD=1.31. High levels of both cognitive reappraisal (4.83) and expressive suppression (4.57) were found in the study as measured by ERQ. Using Pearson correlation, the study revealed a statistical relationship between NSSI and emotion regulation among the respondents with computed p-value= 0.59. Thus, this signifies an aftereffect of improper emotion regulation and the ability to express emotions. The results are recommended to parents and teachers at the very least, to teach their students how to manage and regulate emotions to alleviate the incidence of NSSI.