In this paper, geometric, electric and magnetic properties of graphitic heptazine with embedded Mn atom under bi-axial tensile strain are investigated using density-functional theory with the spin polarized generalized gradient approximation and Hubbard U correction. The binding energy computed for the systems are found to uniformly decrease with the increase in small bi-axial tensile strain (0-5%). The decrease of the binding energy can be related to the increase in the N-C-N bond angle within the cavity which tries to recover its sp(2) hybridized bond. The projected density of states (PDOS) of strained/un-strained systems is also computed. It is found that the covalent bonding of the 6 nitrogen atoms located at the edge of the cavity and the embedded manganese atom in CN1 is mainly contributed by s, d(zx) and d(z2) of the Mn atom, as well as the sp-like orbitals of these nitrogen atoms in the majority spin state respectively. Our calculations also predict enhanced band gap (0.67 eV at zero strain, 1.12 eV at 4% strain) induced by small amount of bi-axial tensile strain. The increase in band gap can be attributed to the structural distortions of the sheet caused by the symmetric deformations which lead to the backward shift in the sigma-like orbitals states of the CN1 atoms. Such properties may be desirable for diluted magnetic semiconductors, future spintronics, molecular magnet and nanoelectronics devices. (C) 2016 Elsevier B.V. All rights reserved.