Inkjet printing is a promising technology because of the material conservation and facile patterning compared with other solution-processed techniques, facilitating the scalable fabrication and commercialization of organic electronics. In this study, organic thin-film transistors (OTFTs) based on poly(3-hexylthiophene) (P3HT) by inkjet printing were fabricated and explored by electrical analysis and morphological characterization. By optimizing the processing conditions, the comprehensive performance in terms of the field-effect mobility of inkjet-printed P3HT-based OTFTs was comparable to those of spin-coated P3HT-based OTFTs. More importantly, with the employment of an electrode buffer layer, namely Br(CH₂)₅N(CH₃)₃Br, the field-effect mobilities of both spin-coated and inkjet-printed OTFTs were improved in accordance with the expectations, resulting from the reduced contact resistance and improved film quality.