We have investigated the influence of inter-vortex interactions on the critical current density (J(c)) and flux pinning properties of single-crystalline MgB2 thin films grown using a hybrid physical-chemical vapor deposition system. Magnetic field dependences of J(c) were measured over a 5-35 K range of temperatures for fields applied parallel and perpendicular to the ab-plane of the film's surface. Two regions along the J(c)(H) curve, the low-field plateau region and the high-field slope region, which are respectively known as the single-vortex and collective pinning regimes, are clearly distinguishable. A ratio a(0)/lambda between the inter-vortex spacing a(0) and the penetration depth lambda was calculated at each temperature, to investigate the effect of vortex-vortex interactions on the J(c)(H). We found that the a(0)/lambda dependences of the normalized J(c)(H,T) data tend to fall onto one curve irrespective of the temperature, if only we use a certain average value of lambda. Furthermore, the flux pinning mechanism shows a crossover from delta T-c-pinning to delta l-pinning with increasing magnetic fields, indicating the coexistence of different pinning mechanisms in MgB2. (C) 2016 Elsevier B.V. All rights reserved.