  Future muon colliders with center-of-mass energy of $\mathcal{O}(1-10)$ TeV
can provide a clean high-energy environment with advantages in searches for
TeV-scale axion-like particles (ALPs), pseudo-Nambu-Goldstone bosons associated
with spontaneously broken global symmetries, which are widely predicted in
physics beyond the Standard Model (SM). We exploit ALP couplings to SM
fermions, and guided by unitarity constraints, build a search strategy focusing
on the ALP decay to top quark pairs at muon colliders. It is found that a large
parameter space of TeV-scale ALPs with TeV-scale decay constants can be probed
by utilizing the ALP-top quark coupling.
