Chaos　is　important　in　nonlinear　science　and　promotes　the　development　of　fundamental　studies,　such　as　neural　networks,　extreme　event　statistics,　and　electron　transport.　In　this　paper,　a　theoretical　scheme　for　generating　dynamical　chaos　in　a　Fabry–Perot　cavity　with　two-level　atoms　is　investigated.　Through　the　injection　of　atoms,　controllable　chaos　of　the　cavity　and　mechanical　oscillator　is　achieved　simultaneously　by　the　external　laser　field.　The　trajectory　and　the　maximal　Lyapunov　exponent　that　characterize　the　properties　of　the　chaos　could　be　optimized　by　adjusting　the　coupling　constant,　driving　field,　injection　of　atoms,　the　frequency　of　the　cavity,　and　the　frequency　of　the　mechanical　oscillator.　This　study　provides　a　new　idea　to　manipulate　the　cavity　and　mechanical　chaos　assisted　by　two　level　atoms.　It　is　hoped　that　the　results　presented　can　benefit　controllable　chaos　generation　and　its applications.　©　2023　Wiley-VCH　GmbH.