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This study developed a facile, highly sensitive technique for extracting and quantifying barbiturates in serum samples. This method combined ultrasound and surfactant‐assisted dispersive liquid–liquid microextraction with poly(ethylene oxide)‐mediated stacking in capillary electrophoresis. Factors influencing the extraction and stacking performance, such as the type and volume of extraction solvents, the type and concentration of surfactant, extraction time, salt additives, sample matrix, solution pH, and composition of the background electrolyte, were carefully studied and optimized to achieve the optimal detection sensitivity. Under the optimized extraction (injecting 140 μL C2H4Cl2 into 1 mL of sample with pH 4 (5 mM sodium phosphate containing 0.05 mM Tween 20 and sonication for 1 min) and separation conditions (150 mM tris(hydroxymethyl)aminomethane‐borate with pH 8.5 containing 0.5% (m/v) poly(ethylene oxide)), the limits of detection (signal‐to‐noise ratio = 3) of five barbiturates ranged from 0.20 to 0.33 ng/mL, and the calculated sensitivity improvement ranged from 868‐ to 1700‐fold. The experimental results revealed excellent linearity (R2 > 0.99), with relative standard deviations of 2.1%–3.4% for the migration time and 4.3%–5.7% for the peak area. The recoveries of the spiked serum samples were 97.1% –110.3%. Our proposed approach offers a rapid and practical method for quantifying barbiturates in biological fluids. [ABSTRACT FROM AUTHOR]