We report measurements of the branching fraction and CP violation parameters in B0→D+D- decays. The results are based on a data sample that contains 535×106 BB̄ pairs collected at the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain [1.97±0.20(stat)±0.20(syst)]×10-4 for the branching fraction of B0→D+D-. The measured values of the CP violation parameters are S=-1.13±0.37±0.09, A=0.91±0.23±0.06, where the first error is statistical and the second is systematic. We find evidence of CP violation in B0→D+D- at the 4.1σ confidence level. While the value of S is consistent with expectations from other measurements, the value of the parameter A favors large direct CP violation at the 3.2σ confidence level, in contradiction to standard model expectations.