A non-intrusive flame to fuel surface radiative heat flux measurement technique is developed using two-color pyrometry of front and side images of upward flame spread along poly(methyl methacrylate) (PMMA). Commercially available Nikon DSLR cameras are radiometrically calibrated to measure soot temperature from the red and green channels of the color images using two-color pyrometry. A 3D ray tracing algorithm is developed to compute radiative heat flux from a sooting flame to the solid fuel surface. Computed heat fluxes are compared to convection corrected Schmidt-Boelter heat flux measurements located at the center of the sample and are shown to be within +/- 65%. To the authors' knowledge, this study is the first attempt to develop a non-intrusive radiative heat flux measurement using DSLR cameras and two-color pyrometry. Flame height estimates using the computed heat flux values are in good agreement with visual observations and prior measurements reported in the literature. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.