Background The HIV cascade of care is a framework for monitoring HIV care, identifying gaps and informing appropriate interventions. This study aimed to describe the cascade of care in Oman in 2019 and highlight disparities at the sub-population level. Methods We used the UNAIDS Spectrum modelling software to estimate the number of people living with HIV. A national HIV surveillance database was used to identify Omani people (13 years old) diagnosed with HIV from 1984 through December 2019. We calculated the cascade indicators as of 31 December 2019 stratified by sex, age, HIV risk factor, residence, and region of HIV care. We also performed multivariate logistic regression to determine the predictors of attrition at linkage, retention, on ART, and viral suppression. Results As of December 2019, the estimated number of people living with HIV in Oman was 2440. Out of the estimated number of people living with HIV, 69% were diagnosed, 66% were linked to care, 61% were retained in care, 60% were on ART, and 55% were virally suppressed. Of the 1673 diagnosed individuals, 96% were linked to care, 88% were retained in care, 87% were on ART, and 81% were virally suppressed. People who received HIV care outside Muscat had the largest attrition (11% loss) in the transition from linkage (97%) to retention (86%). Similarly, people aged 13–24 years had the largest attrition (13% loss) from “on ART” (88%) to viral suppression (75%). Logistic regression showed that both not reporting a specific HIV risk factor and receipt of HIV care outside Muscat independently predicted attrition at each cascade stage from linkage to care through viral suppression. Conclusions Our findings identified substantial disparities across various subpopulations along the cascade of care in Oman.