Halide　perovskites　are　promising　semiconductors　for　inexpensive,　high-performance　optoelectronics.　Despite　a　remarkable　defect　tolerance　compared　to　conventional　semiconductors,　perovskite　thin　films　still　show　substantial　microscale　heterogeneity　in　key　properties　such　as　luminescence　efficiency　and　device　performance.　However,　the　origin　of　the　variations　remains　a　topic　of　debate,　and　a　precise　understanding　is　critical　to　the　rational　design　of　defect　management　strategies.　Through　a　multi-scale　investigation　-　combining　correlative　synchrotron　scanning　X-ray　diffraction　and　time-resolved　photoluminescence　measurements　on　the　same　scan　area　-　we　reveal　that　lattice　strain　is　directly　associated　with　enhanced　defect　concentrations　and　non-radiative　recombination.　The　strain　patterns　have　a　complex　heterogeneity　across　multiple　length　scales.　We　propose　that　strain　arises　during　the　film　growth　and　crystallization　and　provides　a　driving　force　for　defect　formation.　Our　work　sheds　new　light　on　the　presence　and　influence　of　structural　defects　in　halide　perovskites,　revealing　new　pathways　to　manage　defects　and　eliminate　losses.