Due to climate changes, diseases emerging from southerly adjacent areas (Mediterranean countries) are likely to spread northward. Expanded migration of red deer harbors the risk of introducing new pathogens into a naive population of either wild or domestic animals. Little is known about the importance of red deer as a potential reservoir for diseases of domestic ruminants in Switzerland. Deer is susceptible for all three agents that were selected in this study: bovine virus diarrhea virus (BVDV), Anaplasma marginale (AM), and Bluetongue virus (BTV). The goal of this project was to establish the serological status of red deer in Switzerland concerning BVDV, AM, and BTV, and to assess the possible impact of disease dynamics with a focus on potential transmission of these diseases from red deer to cattle or vice versa. Sampling areas were selected according the following criteria: abundance of red deer, potential insect vector distribution due to climatic conditions, and traditional alpine pasture husbandry along with known migration routes of red deer. Blood samples were collected during the regular hunting season 2004 and 2005 by hunters and gamekeepers. There was no serological evidence for the presence of the vector-borne diseases AM and BT in red deer in Switzerland. Four out of 234 sera showed a positive result for BVD, corresponding to a sero-prevalence of 1.7% (95% CI 0.46–4.38). Facing the fact of the high sero-prevalence for BVD in Swiss cattle (60–80%) disease transmission from red deer to cattle in these areas under investigation is rather unlikely.