Development in today's time is increasing rapidly, and the buildings are growing at a rapid pace. To ensure the properties are identified, extensive research is needed to improve the materials used in development. Many methods are used to ensure the strength of a building, such as adding fibers to the building material. The aim of this study is to investigate the use of natural fibers as a reinforcing material in cement brick and to investigate whether the selection of these fibers can contribute to reinforcement or vice versa. This study selected Kenaf Fiber as the main fiber for the reinforcement of cement brick. Therefore, the fiber was also being heat treated in the vacuum furnace under three different temperatures which were 100, 140, and 180 °C at 10 h and non-heat treated to identify the difference in both conditions. The arrangement was also the selection for the main parameters where there were three arrangements, which were bi-directional mat, continuous and aligned and discontinuous and aligned in 50–20 mm length. The are 2 different layers were applied where the first layer consists of 0.2 g weight and the second one consisted of two layers with 0.4 g of weight. For testing the cement brick reinforced with kenaf fiber, the cube samples of 50 mm × 50 mm × 50 mm × 50 mm were cast and tested under the compression machine. The compressive load at a constant rate of 1.0kN/s along the vertical diameter until the failure drops 20%. The cement brick reinforced with kenaf fiber was cured in clean water for 28 and 3 days before testing. Results showed that the non-heat treated kenaf fiber reinforced cement brick was stronger compared to the heat-treated kenaf fiber reinforced cement brick. Moreover, the non-heat treated kenaf fiber reinforced cement brick shows around 6.9% increase of compressive strength compared to plain cement brick. Therefore, the study for the heat treatment determines the maximum mechanical properties of kenaf fiber reinforced in cement brick.