In this proceeding, five key analyses are presented using the full ATLAS Run 2 dataset within the framework of simplified DM models. These models propose that a mediator particle couples to quarks and either SM fermions ( f ) or DM particles ( χ), with possible decays into jets, leptons, or missing transverse energy (Emiss T ). The analyses cover the mono-top search, the dark meson search, a combination of searches within the Two-Higgs-Doublet Model with an additional pseudoscalar mediator (2HDM+a), the dark photon search, and the dark Higgs boson search. While no significant excesses have been observed, the searches place stringent constraints on DM model parameter spaces, guiding the search for potential DM-SM interactions