In this paper, water content and temperature effect on the ultrasonic pulse velocity (UPV) of concrete was investigated. A series of tests were performed to examine the relationship between water content and UPV of concrete with different aggregate mixture proportions. Cube test specimens were made of concrete with water-cement ratio of 0.5. The concrete specimens were immersed in water for 90 days to saturate them. To measure the effect of different water contents on UPV, the test specimens were dried gradually to change the amount of water between measurements. This process was repeated until the concrete pieces was completely dried and weight no longer changed. The water content could be changed from about 6 to 0%. Following, another test procedure was conducted to research the relationship between temperature and UPV. To measure the influence of various temperature on UPV, completely dried concrete specimens were firstly cooled to -18 degrees C and gradually heated to + 180 degrees C. In these two different procedures, the UPV values corresponding water content and temperature in the relevant ranges were periodically measured. The test results indicate that the increase in both water content and temperature increases almost linearly UPV of concrete. Based on correlation derived from the test data, irrespective of concrete properties a further increase in both water content of 1% and temperature of 10 degrees C increases UPV of average 160 and 34 m/s, respectively. As overall assessment, this study demonstrates that the UPV is a function of both water content and temperature, and the changing of these two parameters has an important influence on ultrasonic pulse velocity of concrete.