Residual stress represents one of the most important properties of surface coatings. For DLC films, high compressive stress may cause delamination or limit the deposition of thicker films which are desirable especially for mechanical applications. To overcome adhesion failure, an understanding of stress build-up related to the microstructure is of great importance. For this, DLC thin films were synthesised in an RF (13.56 MHz) asymmetric PECVD reactor using acetylene (C2H2) as a precursor gas. The deposited films were synthesized with different thickness under constant temperature of 200 °C. Pressure and power were fixed at 2.5 Pa and 60 W, respectively. Magnitude of residual stress was obtained from the substrate curvature using the known Stoney's equation. Young's modulus (E) and hardness (H) were derived from nanoindentation data measurements. The microstructure was investigated by Raman spectroscopy between 488 and 514.5 nm. Hydrogen content was measured by nuclear reaction analysis technique. Analysis and discussions of structural characterisation and stress variations with film thickness allowed us to correlate microstructure and mechanical properties to the residual compressive stress.