Dispersive liquid-liquid microextraction in combination with an in situ derivatization is suggested for methyltin compound sampling and preconcentration from water solutions. The derivatization was carried out with sodium tetraethylborate at pH 3. The effects of extraction and disperser solvents type, volume, and extraction time on the extraction efficiency were investigated. 1,2-Dichlorobenzene was used as an extraction solvent and ethanol was used as a disperser solvent. The calibration graphs for all the analytes were linear up to 2 μg (Sn) L(-1), correlation coefficients were 0.998-0.999, LODs were 0.13, 0.05, and 0.06 ng (Sn) L(-1) for trimethyltin, DMT, and monomethyltin, respectively. Repeatabilities of the results were acceptable with RSDs up to 12.1%. A possibility to apply the proposed method for methyltin compound determination in water samples was demonstrated.