Vector-borne diseases transmitted by mosquitoes remain one of the most significant causes of deaths worldwide. With wide cultivation in the Philippines, calamansi (Citrofortunella microcarpa), specifically its peel, was investigated as a potential source of all-natural and organic mosquito repellent. Peel from unripe calamansi was gathered, sundried, and subjected to ethanolic extraction of D-limonene and citral. The distillate was then stored in containers and was sent to DOST-ITDI for determination of D-limonine and citral content concentration and mosquito repellency and knockdown tests. The laboratory test shows that there is 16.8% w/w D-limonene and 15.4% w/w citral content on the sample extracts. The D-limonene content was higher compared to lemon and orange. The highest mosquito repellency effect was observed at 92.5 ± 5% within one minute to less than 5 minutes of the exposure period. The mosquito knockdown effect was also observed starting 20 minutes of exposure period with a 22.5% knockdown. One-hundred residents from Palompon, Leyte, were asked to rate the mosquito repellent, of which 96% said that they would avail the product once commercialized.