We present measurements of the branching fractions B(B0→D*-Ds *+) and B(Ds+→π+), based on 123×106Υ(4S)→BB̄ decays collected by the BABAR detector at the PEP-II asymmetric-energy e+e-B factory. A partial reconstruction technique is used to measure B(B0→D*-Ds*+) and the decay chain is fully reconstructed to measure the branching fraction product B(B0→D*-Ds*+) ×B(Ds+→π+). Comparing these two measurements provides a model-independent determination of the Ds+→π+ branching fraction. We obtain B(B0→D*-Ds*+)=(1.88±0.09±0.17)% and B(Ds+→π+)=(4.81±0.52±0.38)%, where the first uncertainties are statistical and the second systematic. © 2005 The American Physical Society.