Effect of content of hydrogen (H-2) in fuel stream, mole fraction of H-2 (X-H2) in fuel composition, and velocity of fuel and co-flow air (V-avg) on the flame characteristics of a co-flow H-2/N-2 laminar diffusion flame is investigated in this paper. Co-flow burner of Toro et al. [1] is used as a model geometry in which the governing conservation transport equations for mass, momentum, energy, and species are numerically solved in a segregated manner with finite rate chemistry. GRI3 reaction mechanisms are selected along with the weight sum of grey gas radiation (WSGG) and Warnatz thermo-diffusion models. Reliability of the newly generated CFD (computational fluid dynamics) model is initially examined and validated with the experimental results of Toro et al. [1]. Then, the method of investigation is focused on a total of 12 flames with X-H2 varying between 0.25 and 1, and V-avg between 0.25 and 1 ms(-1). Increase of flame size, flame temperature, chemistry heat release, and NOx emission formation resulted are affected by the escalation of either X-H2 or V-avg. Significant effect on the flame temperature and NOx emission are obtained from a higher X-H2 in fuel whereas the flame size and heat release are the result of increasing V-avg. Along with this finding, the role of N-2 and its higher content reducing the flame temperature and NOx emission are presented. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.