The content of the dietary supplements of capsules generated from extracts of medicinal plants in terms of bioactive compounds may not be known. The aim of this study is to do method development and validation for quantification of the phenolic compounds (chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid luteolin-7-o-glucoside, and rosmarinic acid) in capsules of dietary sage (Salvia officinalis) supplements by ultra-high performance liquid chromatography with diode array detector (UHPLC-DAD) to facilitate the quality control. Mobile phase gradient method is optimized in reverse UHPLC mode using aqueous acetonitrile as the mobile and C18 (50*2.1 mm, 1.8 µm) as the stationary phase. Quantitation was done by signal specific integration using diode array detector (DAD). Total run time is 18 minutes. Separation of the phenolic compounds were at 35 °C by employing gradient elution of water: trifluoroacetic acid (100:0.1, v/v) and acetonitrile: water: trifluoroacetic acid (95:5:0.1, v/v/v) as mobile phase A and B, respectively at a flow rate of 0.5 ml/min. The method showed good linearity with correlation coefficient (r2) that varied between 0.9993 and 0.9997. Limit of detection (LOD) and limit of quantification (LOQ) values were 1.97-18.77 and 6.58-62.56 mg/ml, respectively. Recovery (%) were between 90% and 114% for capsule matrix for all compounds at all levels except for ferulic acid and luteolin-7-o-glucoside. The method is suitable for application in quality control laboratories because of the short run time and simultaneous analysis of phenolic compounds in dietary supplements of sage capsules.a