Copper (Cu) powder compacts were sintered by plasma activated sintering (PAS), and the effects of PAS parameters on the densification process of these compacts were investigated. A larger direct current caused a higher rate of temperature increase and therefore a higher densification rate of the Cu powder compact. Under a constant electric current, however, higher mechanical pressure resulted in a lower rate of temperature increase and a lower densification rate of the Cu powder compact. When the applied direct current was the same, the rate of temperature increase of the Cu powder compact after application of a 30-s pulse electric current remained higher than that without a pulse electric current. Application of the pulse electric current before application of the direct current was found to be effective in promoting the densification of Cu powder compacts.