A headspace solid-phase microextraction (HS-SPME) method coupled to GC-MS was developed in order to determine trace levels of tetramethyltin (TeMT) and inorganic tin (iSn) after ethylation to tetraethyltin (TeET) in various matrices. The derivatization of iSn and the extraction of both TeMT and iSn as TeET were performed in one step. Sodium tetraethylborate (NaBEt(4)) was used as derivatization agent and the volatile derivatives were absorbed on a PDMS-coated fused silica fiber. The conditions for the HS-SPME procedure were optimized in order to gain in repeatability and sensitivity. Several critical parameters of GC-MS were also studied. The detection of TeMT and iSn as TeET peaks was performed by the SIM mode. The precision of the proposed method is satisfactory providing RSD values below 10% for both tin species and good linearity up to 10 microg/L. The developed method was successfully applied to the determination of tin species in several samples like canned fish, fish tissues, aquatic plants, canned mineral water and sea water. The proposed HS-SPME-GC-MS method was proved suitable to monitor the concentration levels of toxic tin compounds in environmental and biological samples.