We report a novel method to prepare capsules, beads, or open-cell materials from Pickering emulsions of monomers, stabilized by cellulose nanocrystals (CNCs) grafted with reactive isobutyrate bromide moieties (CNC-Br). CNC-Br particles with different hydrophilic/hydrophobic balance at their surface were prepared and subsequently used to stabilize direct (O/W), inverted (W/O), or double emulsions of styrene or n-BuA. The different emulsions obtained were subsequently polymerized, by initiating an AGET-ATRP polymerization from the brominated particles surrounding the stabilized droplets. The different hybrid polymer materials obtained were subsequently characterized, and the impact of the CNCs functionalization and polymerization conditions was particularly discussed.