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Ab initio calculations showing strain induced bandgap variation in 2D graphene like structure of CdO monolayer is presented in this work. The density functional theory (DFT) calculations were performed using pseudopotential and numerical nano orbitals basis set as implemented in SIESTA. The electron exchange correlation is treated within the local density approximation (CA-LDA). KS-orbitals were expanded based on the double zeta polarization (DZP) with mesh cutoff 250 Ry. The first Brillouin zone was integrated by using 8 x 8 x 1 k-mesh within Monkhorst pack scheme. The optimized lattice parameter was found to be 3.66 □, which is comparable with reported data. Within the compressive strain limit chosen in this work (- 8%), the bandgap remains direct. In the tensile strain, transition from direct to indirect bandgap is observed at 5 % and when the bond length is stretched further, metallic like behavior is observed at 14%, beyond which the conduction band minima falls below the Fermi level. The nature of variation of effective masses of electrons, heavy holes and light holes are calculated from energy bands close to the gamma point, where the band lines are parabolic. While the electrons and light holes effective masses remain almost constant in the range of our calculations, the heavy holes effective masses significantly decreased in the compressive strain and in the tensile strain it significantly increases from its value at the relaxed lattice. Our theoretical predictions in this work will provide valuable information for fabrication of CdO monolayer in nano-electromechanical systems (NEMS) and nano-optomechanical systems (NOMS) devices. [ABSTRACT FROM AUTHOR]