Abstract: Liquid scintillation counting combined with α-spectrometry through measuring ²⁴¹Pu/²⁴¹Am ratio to determine the age of trace Pu was studied. The technique was explored for the age determination of nanogram grade Pu sample on the basis of Pu/Am separation. The ages of two Pu samples—one with known and the other with unknown age were determined by the method. The determined age by the method is in agreement with the reference value. The established method for determining the age of trace Pu can be adopted in the verification activities of nuclear safeguards and nuclear arms control.