Bone　injury　represents　an　urgent　clinical　problem,　and　implantable　bioscaffolds　offer　suitable　means　for　replacing　and　regenerating　damaged　tissues.　This　paper　proposes　an　in-situ　foaming　printing　method　employing　material　extrusion　additive　manufacturing　technology　and　physical　foaming　to　prepared　poly(lactic　acid)/chitin　nanocrystals　(CHNCs)　microporous　composite　scaffolds,　featuring　pore　sizes　ranging　from　9　±　5　μm.　This　method　offers　a　novel　strategy　for　the　preparation　of　poly(lactic　acid)-based　scaffolds　with　good　biocompatibility.　Material　characterization　and　mechanical　property　testing　demonstrated　that　the　in-situ　foaming　printed　PLA　scaffolds　exhibited　excellent　foam　printability,　and　the　expansion　ratio　and　compression　properties　of　the　scaffolds　could　be　adjusted　by　modifying　the　CHNCs　concentration　and　the　printing　speed,　achieving　a　compression　modulus　between　39.2　MPa　and　54.3　MPa.　Furthermore,　at　equivalent　foaming　multiplicity　(1.5–2.6　times),　the　compression　modulus　increased　by　nearly　100　%　compared　to　previously　reported　PLA-based　foam　scaffolds.　Importantly,　the　PLA/CHNCs　scaffolds　produced　via　in-situ　foaming　exhibited　superior　biocompatibility　compared　to　directly　printed　PLA　scaffolds.　This　PLA/CHNCs　composite　scaffold　provides　a　promising　approach　to　addressing　and　repairing　bone　defects.　©　2024　Elsevier　B.V.