This study examined the role of social media language encoding on students interest and performance in essay writing at the University of Port Harcourt. With the rise of platforms like Twitter and Instagram, this form of communication has become increasingly common, especially among youth and students. The population of the study comprised English Studies students of the Faculty of Humanities which totaled 350 students. The sample size consists of 187 students. The purposive sampling technique was used for this study. Two instruments were used for data collection, social media language interest inventory (SMLII) and essay writing performance test (EWPT). The instruments were validated by experts. The reliability of the instruments was done using Cronbach alpha and inter-scorer reliability and the coefficient values of 0.74 and 0.75 were obtained. Research questions were answered using mean and standard deviation, Hypotheses were tested using dependent/paired samples t-test and Analysis of Covariance (ANCOVA) at 0.05 significant level. The results indicated that increased use of social media language encoding impacted students interest and academic performance. Based on these findings, the study concluded that university campaigns could increase awareness of the impacts of social media. Training students in code-switching may also prove beneficial. The study recommended amongst others that students, parents and teachers should harness social media as a tool for strengthening the fluency of English among themselves, their wards and students by patronizing software that fosters the learning of English rather than just chatting away with informal expressions.