Brick and ceramic wastes are becoming one of the most abundantly generated construction and demolition waste (CDWs). However, the practice of utilizing high volume brick and ceramic waste as a precursor and fine aggregate materials in alkali-activated mortar has not yet been exhaustively studied. The main purpose of this research was to analyze the possibility of recycling brick and ceramic wastes as a precursor and fine aggregate in high volume basis in the development of alkali-activated brick and ceramic mortar (AABCM) under ambient temperature. In this respect, waste brick powder (WBP) and waste ceramic sand (WCS) were used as a precursor and fine aggregate, respectively, and ground granulated blast furnace slag (GGBFS) was used to replace WBP in a range of 0–50% at increments of 10% by volume. The AABCM samples were prepared and cured at an ambient temperature for 3, 7, 28, and 56 days: the compressive strength measured in the range of 24–93 MPa and ultrasonic pulse velocity (UPV) values were between 3112 and 4086 m/s indicating AABCM samples were in good condition; both showed improvement when the proportion of GGBFS was increased. The results of this study reveal the strong potential of using brick and ceramics as precursor and fine aggregate materials on a high-volume basis to produce AABCM under ambient temperature conditions.