The main objective of the present study was to improve the productivity of a single-slope solar still using phase change materials (PCM) as a heat energy storage material. Three identical single slope solar stills were constructed and functioned with and without PCM at the Agricultural Engineering Department, Faculty of Agriculture, Suez Canal University, Egypt (latitude angle of 30.62ºN and Longitude angle of 32.27ºE). Paraffin wax was used to store the solar thermal energy in the form of latent heat, which can offer high storage capacity per unit volume, and also due to its feasible general and economic properties. The basin of solar still was rectangular, with a net upper surface area of 1.04 m2. It is painted with matt black paint to absorb the maximum possible amount of solar radiation incident on it. The solar still was covered with glass sheet 3 mm thick and inclined with a tilt angle of 31º of the horizontal plane. The three solar stills (solar still without PCM, solar still with 5 kg PCM and solar still with 10 kg PCM) were examined. The obtained results clarified that, the highest productivity of fresh water (207 ml/ m2 h) was achieved from the solar still with 10 kg PCM followed by the still with 5 kg PCM (182 ml/ m2 h) and the still without PCM (151 ml/ m2 h). The thermal efficiency of the three solar stills with 5 and 10 kg PCM, and without PCM, respectively, was 34.9%, 39.6% and 28.9%. The obtained data also revealed that, the pH (7.46), EC (0.21 ms/cm), and TDS (134.4 ppm) values were lower than those of the brackish water (7.8, 48.5 ms/cm and 31040 ppm, respectively).