We observe a signal for the doubly charmed baryon Ξcc+ in the decay mode Ξcc+→pD +K- to complement the previous reported decay Ξcc+→Λc+K -π+ in data from SELEX, the charm hadroproduction experiment at Fermilab. In this new decay mode we observe an excess of 5.62 events over a combinatoric background estimated by event mixing to be 1.38±0.13 events. The mixed background has Gaussian statistics, giving a signal significance of 4.8σ. The Poisson probability that a background fluctuation can produce the apparent signal is less than 6.4×10 -4. The observed mass of this state is 3518±3 MeV/c 2, consistent with the published result. Averaging the two results gives a mass of 3518.7±1.7 MeV/c2. The observation of this new weak decay mode confirms the previous SELEX suggestion that this state is a double charm baryon. The relative branching ratio for these two modes is 0.36±0.21. © 2005 Elsevier B.V. All rights reserved.