To evaluate the effects of specimen grips on the measurement of the micro-tensile bond strength (mTBS) to dentin. Methods: Twelve extracted human molars were sectioned to expose mid-coronal dentin. Each surface was ground with 600-grit SiC paper. Four adhesives: Prime & Bond NT (Dentsply, USA), Contex (DMG, German), Adper Prompt (3M/ESPE, USA) and Clearfil S3 Bond (Kuraray, Japan) were applied to the polished surfaces followed by creation of composite buildups. After 24 hr storage in 37°C water, the teeth were sectioned perpendicular to the adhesive interface to produce multiple beams of composite-bonded dentin, approximately 0.8 mm2 in cross-sectioned area. Half of the specimens were attached to testing grips A which did not contain positioning pins and another half were attached to the testing grips B which contained positioning pins. All specimens were tested using a universal testing machine at a crosshead speed of 1.0 mm/min. Results: Specimens tested using the grips A presented lower mTBS than using the grips B (P<0.01). Many specimens tested using the grips A showed mix failure or cohesive failure within composite, and most of the failures were adhesive for specimens tested using the grips A. Conclusion: Specimen grips without positioning pins cannot accurately present mTBS and the grips with positioning pins can more accurately present mTBS.