HIV is an independent risk factor for chronic obstructive pulmonary disease; however, baseline risk factors for lung function decline remain largely unknown in this population. HIV-infected participants in the Pittsburgh Lung HIV Cohort with at least 3 pulmonary function measurements between 2007 and 2016 were included. Pulmonary function testing including postbronchodilator (BD) spirometry and diffusion capacity for carbon monoxide (DLco) was performed every 18 months. We used a mixed-effect linear model to evaluate factors associated with pulmonary function testing and DLco decline and logistic regression models to evaluate factors associated with rapid FEV1 decline (defined as >80 mL per year) and any DLco decline. Two hundred eighty-five HIV-infected participants were included. Median baseline CD4 cell count was 521 cells per micro liter, 61.9% had an undetectable HIV viral load at baseline, and 78.5% were receiving ART. Approximately 20% of participants met Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria for a diagnosis of chronic obstructive pulmonary disease at baseline. Older age and baseline GOLD stage 1 compared with stage 0 were associated with faster decline in post-BD FEV1%, whereas female sex was associated with slower decline. Similarly, female sex was associated with slower decline in DLco%. HIV-related factors including CD4 cell count, viral load, and ART use were not significantly associated with pulmonary function decline. Older age, male sex, and higher baseline GOLD stage were associated with more rapid post-BD FEV1% decline in HIV-infected individuals.