We report the first observation of $B^{pm}topsi(2S)pi^{pm}$, a Cabibbo- and color-suppressed decay. This analysis is based on $657times10^{6}$ $Boverline B$ events collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB energy-as
ymmetric $e^+e^-$ collider. The measured branching fraction is ($2.44 pm 0.22 pm 0.20$)$times 10^{-5}$ and the charge asymmetry is $mathcal{A}=0.022 pm 0.085 pm 0.016$. The ratio of the branching fractions $mathcal {B}(B^{pm} to psi(2S) pi^{pm})$$/ mathcal {B}(B^{pm} to psi(2S) K^{pm})$ $ = (3.99 pm 0.36pm 0.17)%$ is also determined.
