Adolescence is a developmental phase largely characterized by rapid biological and non-biological transformations, with a heightened susceptibility to social and environmental influences. Hence, adolescents are particularly vulnerable to external stressors, underscoring the need to safeguard their well-being and prioritize mental health interventions. The coronavirus disease (COVID-19) pandemic caused a global crisis with profound societal disruptions, and led to lasting impact on global public health, disproportionately affecting vulnerable populations, including adolescents. In view of the unique developmental challenges faced by adolescents, it is imperative to assess the growing burden of mental health issues exacerbated by the pandemic. This review synthesizes existing evidence on the emerging mental health challenges faced by adolescents in the United Kingdom (UK) as exacerbated by the COVID-19 pandemic. A systematic literature search was conducted using PubMed, ScienceDirect, MEDLINE, and SpringerNature databases, resulting in the selection of ten high-quality studies. A thematic analysis of the collected data revealed that depression and anxiety were the most frequently reported mental health conditions among adolescents. These conditions were particularly prevalent among adolescents who were from low-income households, those with pre-existing mental health disorders, adolescents experiencing household conflicts, females, and those who provided self-reported data. Several key risk factors were identified, including family and peer relationships, academic pressures such as examinations and grades, financial constraints within households, and the corruptive influence of social media. The findings underscore the urgency of targeted mental health interventions tailored to the specific needs of adolescents in the U.K. By addressing the identified risk factors, mental health professionals, policymakers, and educators can develop more effective strategies to mitigate the psychological impact of the pandemic on this vulnerable population. This study contributes to the evolving body of literature and emphasizes the need for evidence-based policies to foster overall well-being and resilience in adolescents navigating post-pandemic challenges.