Objective: Loneliness is associated with negative mental health outcomes and is particularly common among adolescents. Yet, little is known about the dynamics of adolescent loneliness in non-Western, low-income nations. Accordingly, we estimated the severity of loneliness in a sample of Kenyan adolescents and used mixed-effects regression modelling to determine the socio-cultural factors associated with loneliness. We also used network analysis to examine the associations between loneliness, depression, and anxiety at the symptom-level. Method: We analyzed data from a large sample (N = 2,192) of school-attending Kenyan adolescents aged 1219 (58.3% Female, 41.7% Male). Standardized measures of loneliness (ULS-8), depression (PHQ-8), and anxiety (GAD-7) were used. Results: Our mixed-effects model revealed that female and lower-income adolescents felt lonelier. The perception of feeling alone emerged as the aspect of loneliness most strongly linked to depression and anxiety symptoms. Conclusions: Our findings establish an estimate of loneliness levels in Kenyan adolescents, and reveal sociocultural factors associated with loneliness. We found that perceptions of isolation more strongly linked loneliness to psychopathology than did objective measures of isolation or preferences for social contact. Finally, we identify specific aspects of loneliness that could prove to be treatment targets for youth psychopathology; however, further research is needed. Limitations, future directions, and clinical implications are discussed.