Granular, powdered, and colloidal activated carbons (GAC, PAC, and CAC, respectively) are being used to remove per- and polyfluoroalkyl substances (PFAS) from water. While previous studies have shown that the rate of PFAS adsorption on PAC was larger than on GAC, there has been no direct comparison of PFAS adsorption on PACs versus CACs. Further, there has been no investigation into the relationship between AC size and its ability to adsorb PFAS. To address these knowledge gaps, four commercial ACs (three GACs and one PAC) made from wood, coconut shells, and coal were pulverized by manual grinding followed by micromilling using a bench-top micronizing mill to create PACs (d50=12–107 μm) and CACs (d50=1.2–2.5 μm). The adsorption of either PFBS, PFOA, or PFOS on these adsorbents (11 in total) was investigated using batch solutions containing 0.02–0.2 g/L AC. Under the experimental conditions employed, ∼60% of the outcomes (43 out of 72) showed that less mass of the PFAS explored was adsorbed by CAC than the parent PAC. A detailed characterization of the adsorbent properties (surface area, micropore, and mesopore volumes; pHpzc; and surface elemental composition) suggests that the reduced adsorption capability of the CACs was likely the result of AC oxidation during milling, which decreased surface hydrophobicity. Of all AC types investigated, the materials made from wood possessed the greatest surface area and porosity but adsorbed PFAS the least. The repulsion between the negatively charged surface of wood-based ACs (pHpzc=4.7–5.1) and the negatively charged headgroup of the studied PFAS molecules was identified to be the dominant factor that inhibited adsorption. To our knowledge, this study is the first that systematically investigated the effect of particle size reduction on the ability of ACs of different source materials to adsorb PFAS.