  We study a possibility of a strong first-order phase transition (FOPT) taking
place below the electroweak scale in the context of $U(1)_D$ gauge extension of
the standard model. As pointed out recently by the NANOGrav collaboration,
gravitational waves from such a phase transition with appropriate strength and
nucleation temperature can explain their 12.5 yr data. We first find the
parameter space of this minimal model consistent with NANOGrav findings
considering only a complex singlet scalar and $U(1)_D$ vector boson. Existence
of a singlet fermion charged under $U(1)_D$ can give rise to dark matter in
this model, preferably of non-thermal type, while incorporating additional
fields can also generate light neutrino masses through typical low scale seesaw
mechanisms like radiative or inverse seesaw.
