Concurrent malaria and arbovirus infections pose significant public health challenges in tropical and subtropical regions, demanding innovative control strategies. Here, we describe a strategy that employs multifunctional engineered symbiotic bacteria to suppress concurrent transmission of malaria parasites, dengue, and Zika viruses by various vector mosquitoes. The symbiotic bacterium Serratia AS1, which efficiently spreads through Anopheles and Aedes populations, is engineered to simultaneously produce anti-Plasmodium and anti-arbovirus effector proteins controlled by a selected blood-induced promoter. Laboratory and outdoor field-cage studies show that the multifunctional engineered symbiotic strains effectively inhibit Plasmodium infection in Anopheles mosquitoes and arbovirus infection in Aedes mosquitoes. Our findings provide the foundation for the use of engineered symbiotic bacteria as a powerful tool to combat the concurrent transmission of malaria and arbovirus diseases.