An effective, low solvent consumption, reduced cost and high throughput sample preparation method for the determination of four trihalomethanes (THMs) in tap and swimming pool water samples is presented. THMs extraction and concentration were performed by dispersive liquid-liquid microextraction (DLLME), based on the use of non-halogenated and low volatile solvents as extractants. Analytes were further determined by gas chromatography with micro-electron capture detection (GC-microECD). Under optimized conditions, the proposed method uses 18 mL volume samples, 0.7 mL of acetone (dispersant) and 0.05 mL of 1-undecanol (extractant). Achieved enrichment factors (EFs) varied from 67 to 104 times, the limits of quantification (LOQs) stayed between 0.05 and 1.3 ng mL(-1), and an excellent linearity was noticed up to 100 ng mL(-1). Relative recoveries, measured for spiked aliquots of tap and swimming pool water samples, remained between 79% and 113%, with associated standard deviations below 12%. The applicability of the developed methodology was demonstrated with chlorinated water samples analysis. As regards tap water samples, the sum of THMs concentrations remained under the limit fixed by the European Union (100 ng mL(-1)); however, some samples contained levels close to 80 ng mL(-1), the maximum allowable concentration established by the United States Environmental Protection Agency (EPA).