The effects of source/drain (S/D) electrode material (Ni, Pt and Pd) and deposition method (electron- beam evaporation and sputtering) on the performance of pentacene organic thin- film transistor (OTFT) are studied. Experimental results show that the OTFT with Pd S/D electrodes deposited by sputtering exhibits the best electrical performance. This should be due to the small charge- injection barrier at the pentacene/electrode interface and small thermal load generated during the metal deposition. Besides, through varying the Pd S/D electrode thickness, it is found that increasing the electrode thickness results in performance degradation due to degraded pentacene/electrode interface, which is caused by higher thermal stress developed during longer deposition time.