Blueberry (Vaccinium corymbosum L.) fruits exhibit three growth stages associated with distinct biological processes. During these periods, water and carbon accumulate in the fruit, determining quality traits such as fruit size and sugar concentration. We adapted the Fishman-Genard model to blueberry and used it to analyse the effect of fruit load on fruit fresh mass and water dynamics, based on empirical observations of dry mass and sugar content performed throughout the fruit growth period. Different fruit load treatments were imposed during two seasons on Brigitta' blueberry plants growing under different culture systems. Increasing fruit load significantly reduced the fresh mass of the fruits at harvest, but did not affect sugar concentration, which was simulated and validated with a mean error of 7% for fresh mass and 15% for sugar concentration for the tested conditions. The most sensitive model parameters were those related to cell wall extensibility and sugar uptake. The simulations indicated that larger fresh mass of the fruit was mainly caused by increases in water fluxes rather than pressure differences. The model implementation provides the first estimates of a set of parameters which govern blueberry fruit water dynamics from fruit set to harvest.