Pigeon pea (Cajanus cajan L. Millsp.) is an important grain legume crop of the semi arid tropics and is a major dietary protein source. The extra short duration cultivar of pigeon pea ICPL 88039 was evaluated at ambient
(370 μmol/mol) and twice the ambient (700 μmol/mol) concentrations of CO₂ in open top chambers (OTCs). The results showed that the crop recorded a significant positive enhanced response for total biomass, fodder yield, grain yield, number of pods and seeds per plant, test weight and HI at elevated CO₂. The ANOVA revealed significant differences in response of the characteristics to CO₂ concentrations. Under elevated CO₂ the total biomass recorded an improvement of 91.3%, grain yield 150.1%, fodder yield 67.1%. The major contributing components for improved grain yield under elevated CO₂ were number of pods, number of seeds and test weight which recorded an increase of 97.9%, 119.5% and 7.2%, respectively. The crop maintained a significant positive increase of harvest index (HI) at elevated CO₂ with an increment of 30.7% over ambient values. This increase in HI was due to its improved pod set and seed yield under enhanced CO₂ concentration thereby emphasizes this crop for sustained food with nutritional security under climate change scenario.