Copper-based　chalcogenide　semiconductors　are　particularly　attractive　materials　for　photovoltaic　and　nonlinear　optical　applications.　Unfortunately,　accurate　theoretical　understanding　of　the　optical　responses　of　these　materials　is　hindered　by　the　presence　of　strongly　localized　Cu　3d　electrons.　To　assess　the　validity　of　calculation　schemes　for　determining　the　optical　properties　of　Cu-based　chalcogenides,　different　density　functional　theory　(DFT)　approaches　including　the　conventional　Perdew−Burke−Ernzerhof　(PBE)　method　and　the　modified　Becke-Johnson　(mBJ)　potential　with　and　without　Hubbard　U　correction,　and　the　hybrid　HSE06　methods　are　employed　to　evaluate　the　linear　and　nonlinear　optical　performances　of　16　typical　Cu-based　chalcogenides.　We　calculate　band　gaps,　dielectric　functions,　refractive　indices,　absorption　coefficients,　and　the　second　harmonic　generation　susceptibilities　of　these　compounds　and　compare　the　results　with　available　experimental　measurements.　It　is　clear　that　the　mBJ　+　U　approach　yields　band　gaps　close　to　those　predicted　using　the　HSE06　method,　which　is　consistent　with　the　experimental　values.　More　importantly,　the　fundamental　optical　properties　in　the　infrared-visible　light　region　calculated　within　the　mBJ　+　U　method　agree　better　with　experiments　compared　with　the　HSE06　functional.　In　addition　to　the　linear　optical　responses,　the　mBJ　potential　with　on-site　Coulomb　U　correction　to　the　Cu-3d　state　is　also　capable　of　describing　the　optical　nonlinearity　of　copper　chalcogenides　reasonably.　©　2022　American　Chemical　Society.