Aedes aegypti is a blood-feeding mosquito that transmits human pathogens such as Dengue virus, Yellow Fever virus and Chikungunya virus. Recently, dramatic changes in the transcriptome of Ae. aegypti following a blood meal have been reported; however, the molecular factors involved in regulating these changes are largely unknown. In this study, we found induction of a number of endogenous microRNAs (miRNAs) in blood fed (BF) mosquitoes. One of these miRNAs, aae-miR-375, was only detected in BF mosquitoes. Based on target analyses, we found six different genes involved in development and immunity being regulated by aae-miR-375 at the post-transcriptional level. We further confirmed the specific interaction of aae-miR-375 with the target sequences in the transcripts of two immune related genes, cactus and REL1, using a GFP-based reporter assay. Overall, results from this report indicate that miRNAs induced upon blood feeding can regulate the transcript levels of several genes that are important in development and immune responses in mosquitoes. In addition, we demonstrate that aae-miR-375 enhances Dengue virus serotype 2 (DENV-2) infection in an Ae. aegypti cell line.