The inhibitive effect of Trigonella stellate extract against the corrosion of copper in 1M HNO3 solution has been investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Surface morphology was tested using scanning electron microscope (SEM). The effect of the temperature on corrosion behavior of copper in 1 M HNO3 solution with and without the extract was studied in the temperature range of 25-45oC by weight loss method. Polarization curves revealed that the investigated extract acts as mixed type inhibitor. The inhibition efficiency was found to increase with the increase in the extract concentration and decrease with raising solution temperature. The adsorption of the inhibitor on copper surface was found to obey Timken's adsorption isotherm. The results obtained from different techniques are in good agreement.