Biofuels, such as canola methyl ester (CME), continue to receive considerable attention for their potential use as alternatives to petroleum diesel fuel. The studies on the application of biofuels in internal combustion engines, in general, have shown a considerable reduction in carbon monoxide (CO), soot, and radiative heat emissions, and a small increase in NOx emissions. Radiative heat transfer from flames, which is important in applications such as gas turbines and glass-manufacturing furnaces, has received little attention. The objective of this investigation was to document radiative heat transfer and radical and gas concentration measurements to understand the dominant mechanism of heat transfer in CME/diesel blend flames. In order to isolate the fuel chemical effects on the combustion characteristics of fuels, laminar flames of prevaporized liquid fuels were studied at injector-exit equivalence ratios of 1.2, 2, 3, and 7. Measurements of radiative heat transfer and flame structure including OH and CH radical concentration field were completed. While the peak temperatures in the various blend flames were comparable at the same equivalence ratio, the total flame radiation decreased with the increase in CME concentration in the fuel. Estimates of radiation from gaseous species and soot indicated that about 27–30% of the radiation was from gases, and the rest from soot. The gaseous species contribution to the flame radiation increased slightly with the biofuel content in the blend.