  We present a measurement of the branching fraction for the Cabibbo- and
color-suppressed $B^0 \to \chi_{c1}\pi^0$ decay based on a data sample of
$657\times 10^6$ $B\bar B$ events collected at the $\Upsilon(4S)$ resonance
with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We
observe a signal of $40\pm9$ events with a significance of $4.7\sigma$
including systematic uncertainties. The measured branching fraction is
$\mathcal {B}(B^0 \to \chi_{c1} \pi^0) = (1.12\pm 0.25(\rm {stat.})\pm
0.12({\rm syst.}))\times 10^{-5}$.
