The decay Λb 0→Λc +pp‾π− is observed using pp collision data collected with the LHCb detector at centre-of-mass energies of s=7 and 8 Tev, corresponding to an integrated luminosity of 3 fb−1. The ratio of branching fractions between Λb 0→Λc +pp‾π− and Λb 0→Λc +π− decays is measured to be [Formula presented]=0.0540±0.0023±0.0032. Two resonant structures are observed in the Λc +π− mass spectrum of the Λb 0→Λc +pp‾π− decays, corresponding to the Σc(2455)0 and Σc ⁎(2520)0 states. The ratios of branching fractions with respect to the decay Λb 0→Λc +pp‾π− are [Formula presented]=0.089±0.015±0.006,[Formula presented]=0.119±0.020±0.014. In all of the above results, the first uncertainty is statistical and the second is systematic. The phase space is also examined for the presence of dibaryon resonances. No evidence for such resonances is found.