La0.5Pr0.5Mn2Si2 exhibits an antiferromagnetic-ferromagnetic transition caused by the crossover of the critical distance between Mn atoms on changing temperature. Applying a magnetic field in the antiferromagnetic state can cause a field-induced transformation to the ferromagnetic state at a critical field, which increases with decreasing temperature. We study here with magnetization and strain measurements the magnetic-field-induced strain associated with the field-induced transformation and magnetocaloric effects close to the transition temperature. We also examine the temperature dependence of the critical field and find from magnetization and ferromagnetic resonance measurements that short-range ferromagnetic correlation among the rare earth and Mn-sublattices occur at low temperatures. At low temperatures, this causes a decrease in the critical field for the crossover from antiferromagnetic to ferromagnetic coupling with decreasing temperature.