In concrete, fatigue and freeze-thaw are associated with the progressive growth of internal microcracks. The Ultrasonic Pulse Velocity (UPV) technique, one of the most widely used Nondestructive Testing (NDT) methods, is promising in evaluating internal microcracks and eventually detecting damage. The primary objective of this research was to determine the effectiveness of using UPV to detect damage development in polypropylene fiber reinforced concrete under fatigue and freeze-thaw conditions. In order to realize this, i) several experiments were conducted on control samples to assess the response and limitations of UPV, and ii) fatigue and freeze-thaw samples were tested with UPV to evaluate its ability to detect crack development. In terms of modeling, three alternative models were examined and presented relating UPV with porosity and damage.