In this work, bottom-contact p-type organic thin-film transistors based on small-molecule benzanthracene with various channel lengths were fabricated, characterized, and theoretically investigated. The fabricated devices showed a pronounced shift for threshold voltage as the function of channel length. Electrical parameters characterizing fabricated devices have been systematically evaluated as a function of channel length with and without contact resistance in the calculation. Contact resistance (Rc) and channel resistance (Rch) are extracted individually using the transfer line method (TLM) for output characteristic curves that were done only at low drain voltage (linear regime). The effect of contact resistance on the values of various OTFTs parameters is more pronounced in short channel length devices. The obtained results revealed that the linear regime's corrected mobilities of short channel devices are about 15% smaller than uncorrected mobility. Comparatively, the corrected threshold voltage values were found to be nearly close to uncorrected values for all channel lengths. The analytical model was also applied to reproduce output characteristics in the linear regime of different channel lengths devices with or without contact resistance. It was found that the calculated results were in good agreement with the measured results (when considering the effect of contact resistance), which confirms that the used model can correctly describe the charge transport in these kinds of devices. •Multiple small molecule benzanthracene based OTFTs were fabricated, characterized, and modeled.•Electrical properties of benzanthracene OTFTs were affected by channel length (L) and contact resistance (Rc).•The effect of Rc is more dominant in short-channel device.•Contact resistance corrected-electrical characteristics in linear regime.•Corrected output drain current values with including contact resistance is in good agreement with the measured data.