Multi-frequency transconductance technique is successfully applied in this work for the first time for interface characterization of OFETs. Standard charge pumping measurements are used on silicon MOSFETs for the validation of MFT technique. The method is implemented on pentacene as well as the P3HT based OFETs with SiO₂ as the gate dielectric. Our results show interface state densities in the range of 10¹²/cm²/eV for both the samples. The P3HT films are also shown to have additional trap centres which respond to frequencies above 100 kHz. Our results therefore clearly indicate that the MFT technique is indeed a highly useful technique for interface characterization of OFETs.