Structural, morphological and magnetic behaviour of double perovskite La2-xSrxNiMnO6 (x = 0, 0.3, 0.5) thin films are presented. These films were first optimized and then successfully deposited on substrates of Si (100) by the pulsed laser deposition technique. The (Grazing Incidence x-ray Diffraction) GIXRD observations revealed that all the films are crystalline in nature and exhibit monoclinic structure having a single-phase with P21/n as space group. The grain size, as well as the surface roughness, is found to be decreasing with increasing the strontium (Sr) doping concentration. High-Energy ion scattering (HEIS) spectrometry commonly known as Rutherford Backscattering Spectrometry (RBS) was done on the thin films using He+ ions of energy 2.1 MeV. RUMP simulations of the RBS profiles revealed the precise thickness of these films. Besides, magnetic properties of these films, comprising the coercive field, Curie temperature and the remnant magnetization depend intensely on the concentration of Sr doping.