The result of a search for the decay B-c(+) -> B-s(0)pi(+) is presented, using the B-s(0) -> D-s(-)pi(+) and B-s(0) -> J/psi phi channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1 fb(-1) taken at a center-of-mass energy of 7 TeV, and 2 fb(-1) taken at 8 TeV. The decay B-c(+) -> B-s(0)pi(+) is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is inverted right perpendicular sigma(B-c(+))/sigma(B-s(0))inverted left perpendicular x B(B-c(+) -> B-s(0)pi(+)) = inverted right perpendicular2.37 +/- 0.31 (stat) +/- 0.11 (syst)(-0.13)(+0.17) (tau(Bc+))inverted left perpendicular x 10(-3) the pseudorapidity range 2 < eta(B) < 5, where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the B-c(+) lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction.