The study investigated the effects of adding different types of fibre (psyllium and cellulose) on in vitro digestion behaviour of wheat starch with its thermal and structural properties. Psyllium and cellulose fibres interfered with the wheat starch differently. Psyllium fibre hindered starch gelatinisation, restricted the loss of starch crystallinity, and decreased the accessibility of enzymes to starch. In contrast, cellulose fibre had no significant effect on gelatinisation and loss of crystallinity but limited the digestive enzyme mobility. The impact of psyllium was more pronounced than cellulose on reducing starch digestibility. Rapidly digestible starch fractions of the cooked starch reduced from between 57.90Â±0.60-69.72Â±0.46 (% in starch) to between 28.06Â±0.36-46.34Â±1.10 (% in starch) and 53.23Â±0.36-66.71Â±0.24 (% in starch) for psyllium and cellulose fibre, respectively. This information could be helpful to design foods containing starch with reduced digestibility for a healthy diet. Â© 2021 Institute of Food Science and Technology.