Phosphatidylethanol (PEth) is an alcohol biomarker formed in the presence of ethanol in the body. Both due to its specificity and because it has a detection window of up to several weeks after alcohol intake, its application potential is broader than for other ethanol biomarkers. The aim of this study was to develop and validate a robust method for PEth in whole blood with fast and efficient sample extraction and a short analytical runtime, suitable for high throughput routine purposes. A validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC®-MSMS) method for quantification of PEth 16:0/18:1 in the range 0.05-4.00 μM (R2 ≥ 0.999) is presented. PEth 16:0/18:1 and the internal standard (IS) PEth-d5 (0.55 μM), were extracted from whole blood (150 μL) by simple protein precipitation with 2-propanol (450 μL). Chromatography was achieved using a BEH-phenyl (2.1 × 30 mm, 1.7 μm) column and a gradient elution combining ammonium formate (5 mM, pH 10.1) and acetonitrile at a flow rate of 0.5 mL/min. Runtime was 2.3 min. The mass spectrometer was monitored in negative mode with multiple reaction monitoring (MRM). The m/z 701.7 > 255.2 and 701.7 > 281.3 transitions were monitored for PEth 16:0/18:1 and the m/z 706.7 > 255.3 for PEth-d5. Limit of quantification was 0.03 μM (coefficient of variation, CV = 6.7%, accuracy = 99.3%). Within-assay and between-assay imprecision were 0.4-3.3% (CV ≤ 7.1%). Recoveries were 95-102% (CV ≤ 4.9%). Matrix effects after IS correction ranged from 107% to 112%. PEth 16:0/18:1 in patient samples were stable for several days at 30°C. Repeated freezing (-80°C) and thawing did not affect the concentration. After thawing and analysis patient samples were stable at 4-8°C for at least 4 weeks. Results from a proficiency test program, showing |Z| values ≤1.2, confirm the validity of the method. Analysis of the first 3,169 samples sent to our laboratory for routine use has demonstrated its properties as a robust method suitable for high throughput purposes.