Flavonoids are a widely distributed group of polyphenolic compounds present in an extensive range of edible plants, notably Citrus species. This article reports a rapid, optimized, and validated method for the separation and quantification of flavonoids in three Citrus fruit extracts by ultrahigh performance liquid chromatography (UHPLC) using a photodiode array detector. This new procedure allowed the simultaneous separation and quantification of 11 selected flavonoids in 5.5 min, 8.2 times faster than that by HPLC analysis. The solvent consumption for each individual analysis was also reduced almost 6.2-fold. The most abundant component in the analyzed samples was naringin (299.06-544.36 mg 100 g⁻¹), followed by rutin (116.60-256.33 mg 100 g⁻¹) and quercetin (7.78-251.49 mg 100 g⁻¹). Isoquercitrin was found in a lower proportion (60.05-81.88 mg 100 g⁻¹). The method was completely validated, providing a sensitive analysis for flavonoid detection and showing satisfactory data for all the parameters tested. This methodology is cheaper, more environmentally friendly, and easier to perform than others previously described.