A　near-infrared　(NIR)　photothermal　immunoassay　was　designed　for　the　sensitive　monitoring　of　CA　19-9　on　the　capture　antibody-coated　microplate,　coupling　a　3D-printed　device　with　a　digital　thermometer　in　this　work.　Prussian　blue　nanoparticles　(PBNPs)-encapsulated　CaCO3　microspheres　were　not　only　utilized　for　labeling　of　detection　antibody,　but　used　as　the　photo-heat　conversion　materials　for　the　signal　amplification.　With　the　sandwiched　immunocomplex,　the　as-released　PBNPs　under　acidic　conditions　adsorbed　and　converted　NIR-light　wavelength　to　heat　under　808-nm　laser　irradiation,　thereby　resulting　in　the　temperature　change　of　the　detection　solution.　Under　optimum　conditions,　a　linear　range　from　1.0　U　mL−1　to　100　U　mL−1　and　a　detection　limit　of　0.83　U　mL−1　were　acquired　for　the　CA　19-9　detection　on　the　portable　photothermal　immunosensing　platform　with　PBNP-CaCO3-labeling　system.　Relative　standard　deviations　for　reproducibility　were　≤9.7%　for　intra-assay　and　≤11.9%　for　inter-assay.　High　specificity,　long-time　storage　stability　(＞10　months)　and　good　accuracy　(relative　to　gold　standard　with　commercial　human　ELISA　kit)　with　the　photothermal　immunoassay　were　encountered　for　the　evaluation　of　target　CA　19-9　in　complex　system.　©　2019　Elsevier　B.V.