The main objective of this study is to assess the effect of using social networking site (Facebook) on the user’s psychosocial wellbeing on the preparatory school students. This study has employed both quantitative and qualitative methods. Two hundred sixty six (164 male and 102 female) preparatory school students were selected by using stratified random sampling technique. To collect the data from the participants, five standardized tools were used (Facebook intensity scale, satisfaction with life scale, depression scale, self-esteem scale and social anxiety scale). To analyze the data, the researcher used two way-ANOVA and one sample t-test. The results of the data collection suggest that Facebook user participants had low score in psychosocial wellbeing than their counter parts. Female Facebook users were more vulnerable for low psychosocial wellbeing than males. These finding suggest that the government should establish standardized safe Internet use and harm minimization educational program, provide appropriate alternatives, like sport, educational and recreation facilities for adolescents, and researchers should conduct by including more psychosocial variables with better sample size and better study area.