Drying of agricultural products has always been of great importance for the preservation of food by human beings. Sun drying is a well-known food preservation technique that reduces the moisture contents of agricultural product, and thereby prevents deterioration within a period of time regarded as the safe storage period. Since all fresh tomatoes can not be consumed at the time of harvest, preservation provides a larger market, allowing consumers to buy the preserved tomato around the year. Tomatoes may be dried using either solar energy or mechanical systems. Traditional sun-drying is a slow process compared with other drying methods, but it is said to give dried tomatoes their distinctive quality. Simulation models are helpful in designing new or in improving existing drying systems or for the control of the drying operation. A natural convection solar dryer consisting of a solar air heater and a drying chamber was manufactured in this research. Tomato slices were dried in the solar dryer and compared with open sun drying. Also, tomato slices were dried in a laboratory oven. Effective water diffusivity values ranged from 2.05 × 10 -10 to 7.74 × 10 -11 m 2 /s. The results showed that drying time in the solar dryer is shorter than open sun drying. Shrinkage and rehydration ability of food materials during air drying adversely affects the quality of the dried products. The experimental shrinkage data show a linear behavior with moisture content, with a reduction in sample volume with decreasing moisture content. The effect of temperature on the shrinkage phenomenon can thus be neglected. The experimental data didn't show the dominating effect of temperature on the rehydration ability of this product. The influence of temperature on the rehydration ability can thus be neglected. The drying data as the moisture ratio (MR) versus drying time were fitted to the 13 thin layer drying models. The comparison criteria used to evaluate goodness of fit, namely the coefficient of determination (R 2 ), the root mean square error (RMSE) and the reduced chi-square (? 2 ). The Wang model for oven drying and the Page model for sun drying gave higher R 2 and lower RMSE and ? 2 values than other models. Finally, a numerical model was developed to simulate the moisture transfer during thin layer drying of tomato slices by finite difference method on MATLAB software. The predicted water loss content was validated by comparison with the experimental values (R 2 0.98). It can be concluded that this model describes well the mechanism of moisture diffusion in a one-directional transfer during thin layer drying of tomato slices