SummaryPhenolics bound to dietary fibers (DF‐PCs) represent a valuable source of antioxidants that are often wasted. DF‐PCs can be obtained as residues from conventional extraction processes of PCs derived from agro‐industrial by‐products. This study aimed to characterize DF‐PCs generated after the PC extraction process from the avocado peel (AP), mango peel (MP), and husk mango seed (testa) (MT), with a focus on solid residue or concentrated fiber (APFT: Avocado Peel Fiber; MPFT: Mango Peel Fiber; MTFT: Mango Testa Fiber). The by‐products were evaluated under both non‐defatted and defatted conditions before simulating the PC extraction process. PCs were quantified (TPC) and identified (HPLC‐IDA‐EPI‐MS). Their antioxidant activity (AA) was determined (ABTS+, DPPH*, and FRAP). Among the evaluated fibers, non‐defatted AP and defatted MP and MT exhibited the highest TPC content (22.64 ± 0.3, 37.31 ± 1.78, and 6.07 ± 0.08 mg GAE/g, respectively. Using the DPPH* assay, all fiber concentrates showed lower AA compared to the by‐products. Using FRAP assay, defatting gave the largest activity for mango samples. HPLC‐IDA‐EPI‐MS analysis of PC profiles resulted in the presence of 62 PC compounds in the fiber concentrates. These DF‐PCs, with a significant content of PCs, may be relevant as functional ingredients for food production.