An increased circulation of West Nile virus (WNV) has been reported in Europe during the last decade. Although there have thus far been no reported cases of WNV infections in Belgium, several neighboring countries reported WNV cases in animals and humans, making risk assessments of high importance with regard to a preparedness plan. Therefore we determined the vector competence of field-collected Culex pipiens and Anopheles plumbeus mosquitoes for WNV. Both species could significantly contribute to WNV transmission upon an introduction of the virus due to their proven competence in other countries (Cx. pipiens) and their biting behavior (An. Plumbeus). Mosquitoes were exposed to a blood meal containing 7.13×10^7 PFU/mL WNV (strain Israel 98, lineage 1) and incubated for 14 days at either a constant temperature of 25°C or a 25/15 °C day/night temperature gradient. All mosquitoes were kept at 80% relative humidity, and 16L:8D cycle. Subsequently, infection rate (IR), dissemination rate (DR) and transmission rate (TR) were determined by detection of viral RNA via qRT-PCR in abdomen, head-wings-legs and saliva, respectively. Results indicated that a constant 25°C temperature Cx. pipiens exhibited an IR of 20%, DR of 55%, and TR of 50%, while An. plumbeus showed an IR of 31%, DR of 42%, and TR of 13%, with survival rates of 93% (5⅘8) and 43% (62/143), respectively. These findings suggest that both mosquito species are competent vectors for WNV at 25°C, with overall transmission efficiencies of 5.6% and 1.6%, respectively. For Cx. pipiens, virus isolations confirmed the presence of infectious virus in the collected samples. qRT-PCRs are currently being carried out for the 25/15 °C day/night temperature gradient: the first results show a diminished IR, and a complete absence of dissemination for An. plumbeus, suggesting a temperature-dependent mechanism influencing vector competence. Further analysis will be performed to confirm these preliminary results. Our efforts will provide valuable insights into the dynamics of WNV transmission and inform the development of effective preparedness and control strategies to mitigate the risk of WNV outbreaks in Belgium.