A modified transmission-line method (TLM) for organic field-effect transistors (OFET) contact resistance extraction is proposed. It is shown that the standard TLM approach can provide even the apparent negative contact resistance due to assumption of linear channel-length-dependence of the channel resistance and constant threshold voltage. This can be corrected by the modified TLM, where effect of channel-length-dependent threshold voltage is included with taking into account the dielectric nature of the active layer of OFETs. Obtained results illustrate the need of the threshold voltage discussion for contact resistance evaluation and demonstrate modified TLM approach as more reliable extraction method.© 2014 The Japan Society of Applied Physics.