This study characterized eleven grape pomace varieties from São Paulo and Rio Grande do Sul (Brazil) in terms of proximate composition, total phenolic content, and the total and bioaccessible fractions of inorganic elements and phenolic compounds. On a dry basis, ash, protein, lipid, and carbohydrate contents ranged from 1.4–2.9%, 6.4–13.5%, 8.6–14.7%, and 72.1–83.6%, respectively. Total phenolic content ranged from 567 to 1843 mg GAE/100 g. The contents of essential elements (Ca, Fe, Zn, Cu, Mg, Mn, P, Na, and K) and trace elements (Al, Co, As, Se, Mo, Cd, Sb, Ba, Hg, and Pb) showed wide variation among the varieties studied. Regarding bioaccessibility, low values were observed for Fe, Zn, and Ca, while significant percentages were detected for Mg (27–30%), Mn (1–14%), P (16–26%), Cu (5.5–13%), Co (29–72%), Al (2–13%), and Ba (ND-9%), as well as levels of bioaccessible phenolic compounds (7–19%). The grape pomaces evaluated in this study presented variable levels of total phenolic compounds and minerals, although the bioaccessible fractions varied among the analyzed elements and compounds. These findings contribute to the characterization of Brazilian grape pomaces and indicate their potential applicability as value-added agro-industrial by-products in food formulations, while highlighting the importance of considering bioaccessibility when assessing their nutritional relevance.