Two series of mixed alkali borosilicate glasses have been studied (Na/K and Na/Li) in order to examine the mixed alkali effect influence on the structure evolution of β-irradiated glasses. In both glass series, paramagnetic defects concentration shows a non-linear variation with Na content. The defect nature is also affected and more particularly boron oxygen hole center versus oxygen hole center relative proportion. By Raman spectroscopy, we showed that polymerization increase and molecular oxygen production, linked to the alkali migration, were minimized for some irradiated glass compositions. Mixed alkali effect blocks structural changes under electron irradiation in Na/Li glasses while for Na/K glasses, structural evolutions are smaller than in pure alkali glasses but non-completely annihilated.