The aim of this study was to evaluate the effect of micronization of granulometrically separated olive pomace fractions on dietary fiber composition, technological and functional properties. OP was separated in a 2-mm sieve, resulting in: F1 (>2 mm) and F2 (<2 mm). F2 had higher content of soluble dietary fiber than F1 and lower lignin content. F2 had higher water and oil holding capacities, solubility and cation exchange capacity than F1. The micronization of F1 and F2 fractions using a ball milling (300 r min−1/5 h) reduced the average particle size by 20 times yielding F1AG (17.8 μm) and F2AG (15.6 μm). Micronization caused a redistribution of fiber fractions (from insoluble to soluble), decreased lignin content and changed granule morphology. FT-IR spectra showed that micronization exposed some functional groups, which explains the changes in dietary fiber composition. Thus, micronization converts OP into novel powders bearing improved technological and functional properties. •Granulometric separation of OP fractions produces two novel powders with different compositions.•Micronization increases soluble dietary fiber content of OP fractions.•Micronization reduces lignin content of OP fractions.•Micronization improves physicochemical properties of OP fractions.