Abstract: Abstract. Replacing and repairing cracked concrete can be a costly and time-consuming process that can also be disruptive, with adverse environmental impacts. Taking these challenges into consideration, the current study explores Bacillus subtilis as a bio-admixture to activate an intrinsic self-healing mechanism that allows concrete to heal its cracks by itself. More specifically, the use of Bacillus subtilis ATCC 6633, incorporated into the concrete at a dosage of 2.36 x 109 CFU to heal cracks in the size range of 1-2 mm were tested. Each of the bacteria was assessed at four concentrations—1%, 3%, 5%, and 10% were evaluated for their ability to enhance the self-healing property of the concrete. The self-healing performance and internal structure recovery were assessed using two different methods: the Sorptivity Test (ASTM C 1585) and the Ultrasonic Pulse Velocity (UPV) equipment PUNDIT PL200. The findings revealed that Bacillus subtilis significantly enhanced the self-healing process in 3-7 days, effectively repairing cracks within a 10-day period, as demonstrated by improvements in material recovery, absorption rates, and ultrasonic pulse velocity. The results suggest that 5% Bacillus subtilis concentration has considerable potential to improve the durability and sustainability of concrete, offering a more environmentally friendly and cost-effective solution for autonomous crack repair using the two distinct methods.