We report measurements of branching fractions and time-dependent CP asymmetries in B0→D +D - and B0→D *±D ∓ decays using a data sample that contains (772±11)×106BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e +e - collider. We determine the branching fractions to be B(B0→D +D -)=(2.12±0.16±0.18) ×10 -4 and B(B0→D *±D ∓)=(6.14±0.29±0.50) ×10 -4. We measure CP asymmetry parameters SD +D -=-1.06-0.14+0.21±0.08 and CD +D -=-0. 43±0.16±0.05 in B0→D +D - and AD *D=+0.06±0.05±0.02, SD *D=-0. 78±0.15±0.05, CD *D=-0.01±0.11±0.04, ΔSD *D=-0.13±0.15±0.04 and ΔCD *D=+0.12±0.11±0.03 in B0→D *±D ∓, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of CP symmetry in both decays at equal to or greater than 4σ significance. © 2012 American Physical Society.