The use of veterinary pharmaceuticals in extensive livestock systems raises environmental concern and their detection in environmental matrices requires specific extraction and analytical methods. This study developed a method for simultaneous quantification of six veterinary drugs - benzylpenicillin (antibiotic), acepromazine (sedative), flunixin and dexamethasone (anti-inflammatories), and ketamine and romifidine (analgesics) - in soils, sediments, equine feces, and natural waters. Veterinary pharmaceuticals were extracted from solid matrices by Accelerated Solvent Extraction (ASE) – using a 2:1 (v/v) ultrapure-water/methanol mixture, at 60 °C and 80 °C, with 2, 3 and 4 extraction cycles. The extracts and natural water samples were then purified and concentrated using Oasis HLB®Solid Phase Extraction (SPE) cartridges. Quantification was performed using LC-MS/MS with electrospray ionization, and matrix effects were corrected via isotopically labelled internal standards. Instrumental conditions for both MS (e.g., gas temperatures and flows, energy of collision cell and fragmentation, nebulizer pressure, voltage of exit and capillary) and LC (mobile phase, gradient and chromatography column) were optimized. The method was validated according to the French Standard NF T 90-210. Calibration curves exhibited r²≥0.97, over 1-50 µg.L-1 (acepromazine, flunixin, ketamine and romifidine), 5-100 µg.L-1 (benzylpenicillin) and 2-100 µg.L-1 (dexamethasone). The analytical method demonstrated accuracy within the acceptable deviation of ±30%, at concentrations of 5, 10 and 50 µg.L-1, except for flunixin at 5 and 10 µg.L-1. The method’s limit of quantification ranged from 0.1 to 2 µg.L-1. Overall recoveries for optimized ASE protocols ranged from 38.8 to 94.7% for soils, from 45.3 to 61.4% for equine feces, and from 27.0 to 74.5% for sediments. Oasis HLB® SPE cartridges provided recovery rates of 35.7–90.1%. These performance characteristics demonstrate that these extraction and analytical methods provide a reliable tool for monitoring equine pharmaceutical residues in environmental contexts.