To examine trends and factors associated with isoniazid preventive therapy (IPT) initiation among people living with HIV (PLHIV) aged ≥15 years who initiated antiretroviral therapy (ART) in mainland Tanzania between 2015 and 2020.

A retrospective observational study using routinely collected data. Multilevel logistic regression analysis was used to identify factors associated with IPT initiation.

HIV care and treatment clinics across mainland Tanzania.

The study included PLHIV aged ≥15 years who initiated ART between 2015 and 2020.

The primary outcome was IPT initiation among eligible PLHIV. Secondary outcomes included trends in IPT initiation from 2015 to 2020 and factors associated with IPT initiation.

Among 124 846 PLHIV (mean age 35.8±11.40 years), cumulative IPT initiation was 59.8% (10.50% at first visit; 21.70% within 3 months). Initiation trend increased from 52.70% in 2015 to 68.30% in 2020 (2.05, p

Although IPT initiation among PLHIV in mainland Tanzania improved between 2015 and 2020, coverage remained suboptimal. Strengthened efforts are needed to ensure all PLHIV initiating ART are appropriately screened for tuberculosis (TB), initiated on IPT if eligible and promptly treated if diagnosed with active TB.