We report the first observation of the decay (B) over bar (0)-> D-s(+)Lambda(p) over bar with a statistical significance of 6.6 sigma. We measure B((B) over bar (0)-> D-s(+)Lambda(p) over bar)=(2.9 +/- 0.7 +/- 0.5 +/- 0.4)x10(-5), where the first error is