Mortality and loss to follow-up (LTFU) among adolescents and youth living with HIV (AYLHIV) remain high. We evaluated mortality and LTFU during the test and treat era. We abstracted medical records of AYLHIV for 10-24 years between January 2016 and December 2017 in 87 HIV clinics in Kenya. Using competing risk survival analysis, we compared incidence rates and determined correlates of mortality and LTFU among newly enrolled [<2 years since antiretroviral therapy (ART) initiation] and AYLHIV on ART for ≥2 years. Among 4201 AYLHIV, 1452 (35%) and 2749 (65%) were new enrollments and on ART for ≥2 years, respectively. AYLHIV on antiretroviral therapy (ART) for ≥2 years were younger and more likely to have perinatally acquired HIV ( < 0.001). Incidence of mortality and LTFU per 100 person-years were 2.32 [95% confidence interval (CI): 1.64-3.28] and 37.8 (95% CI: 34.7-41.3), respectively, among new enrollments and 1.22 (95% CI: 0.94-1.59) and 10.2 (95% CI: 9.3-11.1), respectively, among those on ART for ≥2 years. New enrollments had almost twice higher risk of mortality [subdistribution hazard ratio (sHR) 1.92 (1.30, 2.84),  = 0.001] and sevenfold higher risk of LTFU [sHR 7.71 (6.76, 8.79),  < 0.001] than those on ART for ≥2 years. Among new enrollments, mortality was higher in males and those with World Health Organization (WHO) stage III/IV disease at enrollment, and LTFU was associated with pregnancy, older age, and nonperinatal acquisition. Female sex and WHO stage (I/II) were associated with LTFU among those on ART for ≥2 years. During the study period from January 1, 2016, to December 31, 2017, the mortality incidence observed did not demonstrate improvement from earlier studies despite universal test and treat and better ART regimens. This trial was registered with ClinicalTrials.gov, NCT03574129.