This study investigates the impact of social media-induced neologisms on the linguistic proficiency of university students in Cameroon. With the widespread use of platforms like Twitter (now X), TikTok, Instagram, Facebook, and WhatsApp, an increasing number of slang terms and abbreviations—collectively termed neologisms—have become part of students’ daily communication. While these terms foster informal expression and social bonding, their use in academic writing undermines grammatical accuracy, lexical appropriateness, spelling, coherence, and formal tone. Drawing on Halliday’s Systemic Functional Linguistics, particularly Register Theory, this research analyses the written output of 200 first and second year university students, identifying 645 neologism occurrences across 55 distinct types. A coding scheme tracks the frequency, form, and syntactic roles of these neologisms, with attention to their ideational, interpersonal, and textual functions. Additionally, a structured survey explores students’ metalinguistic awareness, language habits on social media, and ability to distinguish between formal and informal registers. Findings show a strong presence of neologisms such as “4u,” “ghosted,” “vibes”, “nerve” and “low-key” in formal assignments, leading to inappropriate register use and reduced clarity. Many students demonstrate "register flattening," struggling to shift between informal digital language and formal academic expression. While the study recognizes the creative and identity-shaping value of social media neologisms, it highlights their unintended negative effects on academic writing standards in the digital age. The research recommends targeted pedagogical interventions to build students’ awareness of language register and promote formal writing skills. Though linguistic innovation reflects cultural change, academic successrequires mastery of formal communication norms; promoting register awareness is therefore essential for maintaining academic standards.