Circulating apolipoprotein-defined lipoprotein subclasses (ADLS) and apolipoproteins predict vascular events in the general and type 2 diabetes populations, but data in T1D are limited. We examined associations of ADLS, serum apolipoproteins, and conventional lipids with carotid intima-media thickness (IMT) measured contemporaneously and 6 years later in 417 T1D participants [men: n = 269, age 42 ± 6 y (mean ± SD); women: n = 148, age 39 ± 8 y] in the Epidemiology of Diabetes Interventions and Complications study, the follow-up of the Diabetes Control and Complications Trial (DCCT). Date were analyzed by multiple linear regression stratified by sex, and adjusted for time-averaged hemoglobin A1C, diabetes duration, hypertension, BMI, albuminuria, DCCT randomization, smoking, statin treatment, and ultrasound devices. In cross-sectional analyses, lipoprotein B (Lp-B), Lp-B:C, Lp-B:E+Lp-B:C:E, Apo-A-II, Apo-B, Apo-C-III-HP (heparin precipitate; i.e., Apo-C-III in Apo-B-containing lipoproteins), and Apo-E were positively associated with common and/or internal carotid IMT in men, but only Apo-C-III (total) was (positively) associated with internal carotid IMT in women. In prospective analyses, Lp-B, Apo-B, and Apo-C-III-HP were positively associated with common and/or internal carotid IMT in men, while Lp-A1:AII and Apo-A1 were inversely associated with internal carotid IMT in women. The only significant prospective association between conventional lipids and IMT was between tria-cylglycerols and internal carotid IMT in men. ADLS and apolipoprotein concentrations may provide sex-specific biomarkers and suggest mechanisms for IMT in people with T1D.