The uniport olfactometer behavioral assay is currently one of the most reliable single-choice methods to use to study mosquito attraction to olfactory stimuli. It allows for the reproducible calculation of mosquito attraction rate to human hosts or to other olfactory stimuli. Here, we present the design of our modified uniport olfactometer. Consistent carbon-filtered air flows through the assay, creating positive pressure that reduces odor contamination from the room. It includes a precision-milled white acrylic base to facilitate easy setup and consistent placement of the component parts. Our design can be made by a commercial acrylic fabricator or an academic machine shop. This olfactometer is designed to assess the responses of mosquitoes but could be applied to other insects that fly upwind toward an odor stimulus. In a companion protocol, we detail how to perform the experiments with mosquitoes by using the uniport olfactometer.