  We point out another important production channel of a light pseudoscalar
Higgs boson $a_1$ via the decays of neutralinos, including
$\widetilde{\chi}_{2,3}^0 \to \widetilde{\chi}_{1}^0 a_1$, in the framework of
the NMSSM. We scan the whole parameter space using the most up-to-date version
of NMHDECAY and search for regions where $B(\widetilde{\chi}_{2,3}^0 \to
\widetilde{\chi}_{1}^0 a_1) > 0.5$. If the gluino and squarks are light enough
for copious production of SUSY events at the LHC, there would be numerous
number of $\widetilde{\chi}_{2,3}^0$ in subsequent decays of gluinos and
squarks. Therefore, the production rates of $a_1$ via neutralino decays would
be more important than $h \to a_1 a_1$ and others. Potentially, the final state
is filled with many $\tau$ leptons, which can be reconstructed at the mass of
$a_1$. This is a clean, observable, and distinguishable signature for NMSSM.
