HIV-associated functional impairment may cause cognitive impairment secondary to the viral infection, hence, associations between cognitive impairment and functional impairment in youth living with HIV are important to assess. We sought to determine whether cognitive impairment is associated with functional impairment and if it carries higher risk for also having functional impairment. We collected parent-rated information regarding youth functional impairment on four different measures and administered a cognitive battery to youth to determine cognitive impairment, 203 HIV-infected youth and 44 HIV-uninfected controls. Degree of cognitive impairment correlated strongly with decreased function: CBCL,  = -.17,  = .01; VABS2,  = -.28,  < .001; repeated-grades,  = .26,  < .001. Presence of cognitive impairment was associated with increased risk of functional impairment: 3.47 (CIS); 1.71 (CBCL); 2.17 (VABS2); 2.97 (repeated-grades). Repeated-grades strongly associated with cognitive impairment and functional impairment. We found strong associations between HIV-infected youth functional impairment on CBCL, VABS2 and repeated-grades with degree of cognitive impairment; and that when cognitive impairment was present youth had higher risk of experiencing functional impairment as well. Asking whether youth have repeated a grade at school could be a helpful screening question for assessing potential functional impairment and provide clinicians with an indication as to whether a further in-depth assessment is required.