In this study, mass transfer during osmotic dehydration of blackberry in sugar solution was investigated. The osmotic solution concentrations used were 40%, 50% and 60% (w/w) sugar, osmotic solution temperatures used were 30 ℃, 40 ℃ and 50 ℃, the solution-to-blackberry mass ratio was 10:1 (w/w) and the process duration varied from 0 to 5 hr. A two-parameter mathematical model developed by Azuara et al. was used for describing the mass transfer in osmotic dehydration of blackberry samples and estimation of the final equilibrium moisture loss and solid gain. The results showed that the dehydration rate and solid gain rate of blackberry were increased with the increase of osmotic concentration, osmotic time and temperature of the solution under certain experimental conditions. Effective diffusivity of moisture as well as solute was estimated using the analytical solution of Fick’s second law of diffusion. For above conditions of osmotic dehydration, moisture and sugar effective diffusivities were found to be in the range of 1.77×10-9-2.10×10-9and 1.36×10-9-1.60×10-9m2/s, respectively.