Resistance of steel and reinforced concrete (RC) beam-to-column connections to blast loading is presented in this paper. The steel and RC connections are analysed nonlinearly using the finite element (FE) software ABAQUS. Comparisons of the obtained results from the connections modelling with those of the experimental tests reveal the modelling accuracy. Then, the ETABS software is utilised to design 4 buildings including 2 steel buildings with 5 and 9 storeys and 2 RC buildings with the same number of storeys. The components of the selected beam-to-column connections of the ground floor of the buildings are designed. Then, different parameters are considered for the nonlinear analyses of the steel and RC connections. The studied parameters for the steel connections are as the size of cross-section, bolts arrangement, and using stiffeners in the beam web of the connections, while the parameters for the RC connections are as the size of cross-section, stirrups space, and making beam non-prismatic in the beam-column connection region. It was found that increasing the cross-sectional sizes of the beams and columns of the steel and RC connections considerably enhances the resistance of the connections. In addition, change of the bolts arrangement in the steel connections and reducing the stirrups space in the RC connections significantly influence the resistance of the connections. However, using stiffeners in the beam web of the steel connections and making the beam non-prismatic in the region of the beam-column RC connections have no remarkable effect on the connections resistance. Failure modes of the connections are also evaluated.