A fast and selective ultraperformance liquid chromatographic-tandem mass spectrometric method was developed and validated for the simultaneous quantification of amitriptyline, citalopram, clomipramine, desipramine, desmethylcitalopram, desmethylclomipramine, desmethyldosulepin, desmethyldoxepin, desmethylfluoxetine, desmethylvenlafaxine, didesmethylcitalopram, dosulepin, doxepin, duloxetine, fluoxetine, fluvoxamine, imipramine, maprotiline, mianserin, mirtazapine, moclobemide, nortriptyline, paroxetine, reboxetine, sertraline, trazodone, and venlafaxine in 100 μL of plasma. After liquid-liquid extraction with 1-chlorobutane, analytes were separated on a BEH (Ethylene Bridged Hybrid) C18 analytical column with gradient elution. The compounds were ionized and detected over 7-minute analysis time by electrospray ionization tandem mass spectrometry with multiple reaction monitoring. Limits of quantification and limits of detection ranged from 2.5 to 10 ng/mL and 0.2 to 10 ng/mL, respectively. Intra- and interassay imprecision were lower than 15% for all the compounds except for mirtazapine, moclobemide, and desmethylclomipramine [relative standard deviation (RSD) < 20%], and the bias of the assay was lower than 15% for all the compounds except for fluvoxamine (bias < 20.5%), evaluated with 5 commercial quality control and 3 "in-house" quality control. The extraction was found to be reproducible (RSD < 16%) (except for duloxetine RSD 21.9%) and with recoveries varying from 59% to 86%. Furthermore, the stability studies demonstrated that the processed samples were stable in the autosampler for 24 hours for all the compounds. The method was successfully applied to the analysis of authentic samples from forensic toxicology cases and external quality control assays from the Society of Toxicology and Forensic Chemistry (GTFCh). The method was completely validated and can be of interest to clinical and forensic laboratories.