Mixed-viral infections of heterologous viruses such as Potato virus Y (PVY) (Potyviridae: Potyvirus) and Potato leafroll virus (PLRV) (Luteoviridae: Polerovirus) are a regular occurrence in Idaho’s potato, Solanum tuberosum (Linnaeus) cropping systems. Laboratory studies were conducted to examine the effect of mixed-viral (PVY-PLRV) infection on the fecundity and preference of two of the most efficient PVY and PLRV vectors, the green peach aphid, Myzus persicae (Sulzer), and the potato aphid, Macrosiphum euphorbiae (Thomas), (Homoptera: Aphididae). Myzus persicae and M. euphorbiae fecundity was significantly higher on mixed-infected plants than on singly-infected plants or non-infected plants. Preference of winged and wingless M. persicae and M. euphorbiae was determined with the use of settling bioassays. Both winged and wingless M. persicae and M. euphorbiae preferentially settled on PVY-PLRV infected plants than on singly-infected plants (PVY or PLRV) or non-infected plants.