  Recently, the MiniBooNE experiment at Fermilab has updated the results with
increased data and reported an excess of $560.6 \pm 119.6$ electronlike events
($4.7\sigma$) in the neutrino operation mode. In this paper, we propose a
scenario to account for the excess where a Dirac-type sterile neutrino,
produced by a charged kaon decay through the neutrino mixing, decays into a
leptophilic axionlike particle ($\ell$ALP) and a muon neutrino. The
electron-positron pairs produced from the $\ell$ALP decays can be interpreted
as electronlike events provided that their opening angle is sufficiently small.
In our framework, we consider the $\ell$ALP with a mass $m^{}_a =
20\,\text{MeV}$ and an inverse decay constant $c^{}_e/f^{}_a =
10^{-2}\,\text{GeV}^{-1}$, allowed by the astrophysical and experimental
constraints. Then, after integrating the predicted angular or visible energy
spectra of the $\ell$ALP to obtain the total excess event number, we find that
our scenario with sterile neutrino masses within $150\,\text{MeV}\lesssim
m^{}_N \lesssim 380 \,\text{MeV}$ ($150\,\text{MeV}\lesssim m^{}_N \lesssim 180
\,\text{MeV}$) and neutrino mixing parameters between $10^{-10} \lesssim
|U_{\mu 4}|^2 \lesssim 10^{-8}$ ($3\times 10^{-7} \lesssim |U_{\mu 4}|^2
\lesssim 8 \times10^{-7}$) can explain the MiniBooNE data.
