  The gluon distributions of the pion obtained from various global fits exhibit
large variations among them. Within the framework of the color evaporation
model, we show that the existing pion-induced $J/\psi$ production data, usually
not included in the global fits, can impose useful additional constraints on
the pion parton distribution functions (PDFs). In particular, these data can
probe the pion's gluon densities at large $x$. Existing pion-induced $J/\psi$
data covering a broad range of beam momenta are compared with
next-to-leading-order QCD calculations using various sets of pion PDFs. It is
found that $J/\psi$ data measured at forward rapidity and at sufficiently high
beam momentum are sensitive to the large-$x$ gluon distribution of pions. The
current $J/\psi$ data favor the Sutton-Martin-Roberts-Stirling and
Gluck-Reya-Vogt pion PDFs, containing significant gluon content at large $x$.
