Microsphere　(MS)　cavities　hold　great　potential　in　nanophotonics　due　to　their　extraordinary　optical　properties.　All-inorganic　trihalide　perovskites　with　high　environmental　stability　and　easy-for-preparation　have　shown　great　promise　for　the　next-generation　optoelectronic　nanodevices.　Unfortunately,　the　nonradiative　recombination　of　exciton　is　inevitably　aggravating　the　photoluminescence　quantum　yields　(PLQYs).　Here,　a　microsphere-coupled　CsPbBr3　perovskite　vertical　structure　is　proposed　for　amplification　of　spontaneous　radiation　(SR)　up　to　190-fold.　The　mechanisms　of　SR　amplification　by　an　MS　cavity　are　completely　revealed,　for　the　first　time,　including　Mie　focusing　(MF)　for　energy　harvesting,　directional　antenna　(DA)　for　emission　convergence,　and　whispering-gallery　modes　(WGMs)　for　regulation　of　exciton　dynamics.　The　temperature-dependent　photoluminescence　(PL)　spectra　clarify　the　contributions　of　WGMs　for　the　boosting　of　SR　decay　and　suppression　of　exciton–phonon　interactions　for　giant　PL　enhancement.　Furthermore,　a　straightforward　approach　is　presented　for　a　selective　MS　array　capped　on　a　perovskite　microcrystal　(PeMC)　film　as　a　vertical　structure　for　patterned　PL　enhancement.　The　excitation-power-　and　excitation-observation-angle-dependent　luminescence　contrast　inspire　a　novel　anticounterfeiting　strategy.　The　vertical　architecture　not　only　advances　the　understanding　of　microcavity-based　SR　amplification　from　PeMCs,　but　also　offers　opportunities　to　facilitate　the　synergistic　manipulation　of　optical　fields　and　exciton–phonon　interactions　for　developing　high-efficient　optoelectronic　devices.　©　2021　Wiley-VCH　GmbH