Using the data sample of 711 fb −1 of ϒð4SÞ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays B − →Λ − c Ξ 00 c , B − →Λ − c Ξ c ð2645Þ 0 , and B − →Λ − c Ξ c ð2790Þ 0. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling againstΛ − c baryons in selected B − candidates. The branching fraction of B − →Λ − c Ξ c ð2790Þ 0 is measured to be ð1.1 AE 0.4 AE 0.2Þ × 10 −3 , where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on BðB − →Λ − c Ξ 00 c Þ and BðB − →Λ − c Ξ c ð2645Þ 0 Þ are determined to be 6.5 × 10 −4 and 7.9 × 10 −4 , respectively.