In several developing countries, construction materials have increased immensely due to rapid urbanization, leading to extremely high demand for natural resources. In general, many countries rely on concrete as their main construction material. Therefore, the demand for natural resources, including cement, fine aggregate, and coarse aggregate, continues to rise. In addition, the agricultural sector works to sustain the economy and provide the essential needs of the communities. This sector produces various wastes that have not been utilized sufficiently. This study attempted to utilize agricultural waste as a substitute for fine aggregate in cement mortar. The agricultural waste is used from the sugarcane farm (bagasse ash), the rice farm (rice husk ash), and the corn farm (cob corn ash). Utilization of this waste aims to reduce the use of sand as fine aggregate for the production of mortar and to increase the amount of agricultural waste to be utilized sufficiently. Experiments on the laboratory scale were conducted to measure the fresh and hardened properties of cement mortar. Fresh properties were evaluated using the slump flow test, while hardened properties were evaluated by compressive strength, porosity, water absorption, and mass loss. In addition, non-destructive tests, including rebound hammer and ultrasonic pulse velocity tests, were also conducted. This investigation indicates that introducing agricultural waste for additional mortar materials can improve its compressive strength and other properties. However, appropriate mix proportions are required to produce high-performance mortar.