We report on the observation of the Cabibbo-suppressed mode
B^+ -> J/psi pi^+, with J/psi -> mu^+mu^-.  Further, we calculate the
relative branching ratio, BR(B^+ -> J/psi pi^+)/BR(B^+ -> J/psi K^+) and
find a value of (4.9^+1.9_-1.7 \pm 1.1)%.