Tomato yellow leaf curl virus (TYLCV) and Tomato mottle virus (ToMoV) (Geminiviridae, Begomovirus) are two tomato-infecting viruses. TYLCV is one of the most damaging pathogens of tomato, and it limits production of tomato worldwide. Though viruses are usually studied as a single infection, mixed viral infections have become a major problem in agriculture. Mixed infections of plant viruses can be important factors in influencing disease severity, genetic diversity of the co-infecting viruses, transmission rates, and virus evolution. The role of the vector in propagating mixed infections has been largely ignored. In this study, we investigated the role of vector transmission on the propagation of single and mixed infections of TYLCV and ToMoV by its whitefly vector, Bemisia tabaci, in tomato. A transmission experiment was designed to investigate how acquisition of these viruses together in mixed infections or sequentially in single infections by B. tabaci influences the probability of transmission. After whitefly transmission, plant heights and disease severity scores were recorded 7, 14, 21, and 28 Days Post Inoculation. At 28 DPI plant samples were collected from all plants and virus infection confirmed using PCR. Results from these experiments will be presented.