The impact of sourdough amount (20, 40 and 60%) on the rheological behaviour of gluten-free chestnut-rice dough formulations and quality parameters (pH, total titratable acidity, firmness, volume and crumb microstructure) of the corresponding breads was studied. The addition of sourdough led to decreases in complex modulus indicating a softening of the dough samples. Higher levels of sourdough addition had a detrimental effect on the volume and texture of breads. X-ray micro computed tomograph images showed that gluten-free chestnut-rice breads prepared with a sourdough incorporation of 20% had the most homogenous structure with high number of smaller pores. Inferior crumb structures were observed with the further addition of sourdough. Confocal laser scanning microscopy revealed that the proteins in breads prepared with sourdough were smaller due to their degradation into smaller peptides by the sourdough fermentation. These changes resulted in an improvement of the bread quality.