© 2015 IEEE. As the diameter of semimetal nanowires decreases semimetal to semiconductor transition occurs as a consequence of quantum confinement. This enables the use of bandgap engineering to form a field-effect transistor near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain for sub-5 nm transistors. The use of strain as a 'technology booster' in transistor design has been used in Si technology; in this study the electronic structure of tin nanowires (SnNW) under uniaxial strain is investigated using density functional theory (DFT). Also, the valence and conduction charge density modification under applying uniaxial strain is studied. It is demonstrated that the properties of a 4.2 nm -oriented SnNW varies towards more metallic or semiconducting by the application of tensile or compressive strain, respectively. Strain energies and Young modulus which vary with nanowire diameter and crystal orientation are also analysed. It is demonstrated that strain can be applied in addition to geometry confinement to tune the bandgap and other electronic properties.