The "compensatory feeding hypothesis" proposes that herbivorous insects may increase their plant consumption to compensate for the deficiency of Nitrogen in the plant tissue consumed under elevated CO₂ concentration. The empirical studies however are not overall in line with this prediction. In this study laboratory trails were conducted in growth chambers by manipulating CO₂ concentration (390μL/L, 780μL/L) and the nitrogen-fixing bacteria (NFB) (with, without) for the common bean Phaseolus vulgaris in a factorial design. Prodenia litura larvae at the 4^th stadium were fed with the bean plants cultured in aforementioned treatments, and testedfor food consumption and utilization. ANCOVA results showed that CO₂ and NFB had significant effects both independently and in interaction on the 4^th instar larva in relative consumption (RCR) and relative growth rate (RGR). Under ambient CO₂ there were no differences in RCR and RGR between NFB treatments, but in elevated CO₂ RCR and RGR increased in the absence as opposed to the presence of NFB. CO₂ and its interaction with NFB had significant influence on approximate digestibility (AD), where AD increased in elevated CO₂ as opposed to ambient CO₂ in the absence of NFB but slightly reduced in the presence of NFB. CO₂ and NFB treatments did not influence efficiency of conversion of ingested food (ECI). The results of this study lend support for the prediction of the compensatory feeding hypothesis.