The present study was conducted to screen 19 genotypes of Mahaneem (Ailanthus excelsa Roxb.) and to identify the best performing genotypes under arid ecosystem of Haryana, India. Among the genotypes, ‘S-9’ and ‘S-18’ performed consistently with higher growth and carbon sequester as compared to other genotypes. The maximum plant height and girth at breast height was 9.91m and 65cm respectively, in ‘S-9’ after 8 years of planting, which was at par with 04 genotypes (‘S-4, S-6, S-11 and S-18’) over other selections. At 4 and 8 year after planting of A. excelsa, ‘S-9’ produced the highest biomass production i.e., 0.66 tones per tree over all the genotypes. The maximum mean values of dry matter accumulation/ plant were 0.52 tones/ tree recorded after 8 year of planting in S-9 genotypes. Similar results for CO2 equivalent, which was significantly higher in S-9 i.e., 0.96 tonnes per tree after 8 years of planting over other genotypes of A. excelsa. The overall results revealed that the genotypes ‘S- 9’ and ‘S- 18’ were identified as the best genotypes for multiplication in the field to increase the biomass production and CO2 equivalent for the arid regions.