Since the inception of differentiated care in Kenya in 2017, patient categorization at enrolment has been based on the CD4 counts and WHO staging as either well or advanced. The DC operation manual offers separate package of care for the two categories of clients with the advanced category getting preferential management, and little is known of the impact of this on treatment outcomes. The purpose of this study was to investigate the effect of categorization at enrolment between October 2018 and September 2019, using 182 HIV patient records and 7 key informant interviewees on treatment outcomes 12 months later in Nyatike Sub County. The focus was on retention to care, viral load suppression, morbidity and mortality. Sample size got by mixed methods and quantitative data analyzed by Chi-square tests and Fischer’s exact test where applicable, used to test for association between predictor and outcome variables with risk ratios applied to quantify significant associations. Associations were presented as adjusted risk ratios (aRRs), with 95% CIs. Statistical analysis tests conducted at 5% level of significance while qualitative data was analyzed by generation of themes, and results triangulated with the quantitative data. Categorized as well, were 134(74%) client records while 48 (26%) were advanced. Retention was better among advanced category at (71%) compared to the well (64%) group; however, retention on ART was not associated with DC categorization with RR of 0.96 (0.73 - 1.13). Viral load suppression in the well group was 97% (87/90) compared to 92% (34/37) for the advanced category. There was however no statistical significant association between Viral suppression and categorization [aRR 1.05 (0.95 - 1.17)]. Opportunistic Infection incidence was higher among the advanced category (79% vs 3%, unadjusted risk ratio RR 0.04, 95% CI: 0.01 – 0.10), with higher risk of contracting an OI even after adjusting for age, sex, and WHO staging [aRR (95% CI) = 0.04 (0.02 – 0.13)]. The Ministry of Health should institute measures that improve retention to care and viral load uptake and suppression, while restructuring the model of care that will serve all clients equitably and reduce morbidity and mortality in PLHIV.