Poisson's ratio (nu) of Asphalt Concrete (AC) is a fundamental input parameter to any numerical analysis based on elastic and viscoelastic constitutive properties. To this date, temperature-and time-dependent nu-value has been determined by either a static or a relaxation test at a single temperature in diametrical mode. This study, for the first time, performs relaxation tests at different temperatures in diametrical mode. In addition, cyclic load testing is conducted at different temperatures and loading frequencies to determine the temperature- and frequency-dependent nu-value of AC. Relaxation test results show that the nu-value of AC increases with testing time and temperature. Dynamic load test results show that nu-value of AC decreases with loading frequency; however, increases with temperature. To this end, measured nu-value of AC is compared with the nu-value predicted using model available in the new AASHTOWare Pavement Mechanistic-Empirical (ME) Design software. The measured nu-value matches with the predicted nu-value by the AASHTOWare Pavement ME Design software especially for AC that possesses high dynamic modulus. (C) 2015 Elsevier Ltd. All rights reserved.