The laminar burning speed of spherically expanding flame for propane (C₃H₈) and carbon dioxide (CO₂) mixtures with air were measured experimentally under stoichiometric conditions over a range of pressures (1 atm to 6.2 atm), temperatures (298 K to 420 K), and CO₂ concentrations (0% to 60%). Experiments were conducted in a cylindrical chamber with a Z-shaped Schlieren system coupled with a high-speed CMOS camera that was used to capture the evolutionary behavior of flames at speeds up to 40,000 frames per second. Only flames that were completely laminar, smooth, and spherical were used to calculate the laminar burning speed. Pressure rise as a function of time during the flame propagation was the primary input of the multi-shell thermodynamic model used to calculate the laminar burning speed. The laminar burning speed was observed to decrease with the dilution of CO₂. Laminar burning speed results were calculated for various C₃H₈/CO₂/air mixtures to determine the effects of mixture proportions on the laminar burning speed.