Abstract Dislocation junctions are considered to control the hardening behavior of crystalline materials during plastic deformation. Here the influence of the glissile junction on the plastic deformation of microscale samples is investigated, based on discrete dislocation dynamics simulation results. It is found that with increasing dislocation density ρ , sample size d, which can be collapsed into a single dimensionless parameter d ρ , and an increasing number of activated slip systems due to different global crystallographic orientations, the glissile junction forms frequently and can bow out easily, acting as an effective source. The resulting new dislocations are mobile and contribute to the macroscopic plastic deformation on the order of 30–60%. In the size regime from 0.5 to 2 μm and dislocation densities in the range of 10^12 – 10^14 ^ -2 , the glissile junction is therefore an important source for generating mobile dislocation density. Furthermore a significant correlation between stress drops and activity of dislocations originating from glissile junctions is found. A rate formulation is proposed to include these findings in crystal plasticity or continuum dislocation density frameworks.