The effect of the addition of hydrogen to various multicomponent natural gas (NG) blends is experimentally and numerically investigated. All the experiments are performed at a pressure of 0.1 MPa, a temperature of 300 +/- 3 K, and a range of equivalence ratios (Phi = 0.6 to 1.4), using a constant pressure freely propagating spherical flame method. Numerical simulations are performed using the CHEMKIN-PRO (R) simulation software, with three different chemical kinetic mechanisms. Laminar burning velocity (LBV) and burned gas Markstein length (L-b) of the various NG-H-2 blends at three different levels of hydrogen in the fuel, viz., 25%, 50%, and 75%, are experimentally evaluated to assess the effect of the simultaneous presence of H-2 and higher hydrocarbons (HC) in various NG blends. The addition of H-2 enhances the combustion chemistry of all the NG blends, and hence, increases the LBV. However, the effect is more prominent for the NG6-H-2 blend, which has a higher mole fraction of CH4. The NG5-H-2 blend, which has a higher mole fraction of C3H8 maintains a positive Lb for a wider range of equivalence ratios (0.7-1.4). The LBV prediction using the GRI-MECH 3.0 mechanism is within the range of experimental uncertainty, for the blends with up to 50% H-2 in the fuel. The prediction of LBV using GRI-MECH 3.0 is the closest to the experimental results for the blends with 75% H-2 in the fuel when compared with those using San Diego and USC-MECH 2.0 mechanisms. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.