We report the first observation of B{sup {+-}}{yields}{chi}{sub c1}{pi}{sup {+-}}, a Cabibbo- and color-suppressed decay in a data sample of 386x10{sup 6} BB events collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We observe 55{+-}10 signal events with a statistical significance of 6.3{sigma} including systematic uncertainties. The measured branching fraction and charge-asymmetry is B(B{sup {+-}}{yields}{chi}{sub c1}{pi}{sup {+-}})=(2.2{+-}0.4{+-}0.3)x10{sup -5} and A{sub {pi}}=0.07{+-}0.18{+-}0.02, respectively. We also determine the ratio B(B{sup {+-}}{yields}{chi}{sub c1}{pi}{sup {+-}})/B(B{sup {+-}}{yields}{chi}{sub c1}K{sup {+-}})=(4.3{+-}0.8{+-}0.= 3)%.
