Measurements of CP violating phases provide valuable tests of the flavour sector in the SM and offer opportunities to search for signs of beyond-SM physics. The LHCb experiment has measured mixing-induced CP violation in various $B^0$ decay modes using proton-proton collision data, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected at $\sqrt s$ = 7 and 8 TeV. In this talk latest results on $B^0 \to J/ \psi K_S$, $B^0 \to D^+D^-$ and $B^0 \to J/ \psi \pi^-\pi^+$ decays are reported. The measurements of the CP violating phases are presented and the contributions due to tree-level and loop processes are discussed.