Whole grains are associated with decreased risk of chronic disease and decreased risk of obesity. Several mechanisms may be involved including SCFA production via fibre fermentation in the colon. The aim of the present study was to evaluate the role of wheat bran particle size (large/coarse v. small/fine) and wheat bran fraction (whole bran v. aleurone v. aleurone by-product) in SCFA production using a batch in vitro fermentation system with human faecal inoculum. Five samples were compared: large-particle bran, small-particle bran, aleurone, coarse by-product, fine by-product. Fine by-product produced the greatest SCFA concentrations. By-product (both coarse and fine) produced greater SCFA concentrations than bran (both large and small particle sizes). Aleurone produced SCFA concentrations similar to small-particle bran. The molar percentage of butyrate at 24 h was significantly greater for large-particle bran than the other samples. Small/fine particle size and by-product fraction of bran increased SCFA production compared with large/coarse particle size, and aleurone and whole bran. Bran characteristics and composition should be considered when manufacturing foods due to the diversity of physiological effects.