Herein,　we　presented　a　dual-readout　gasochromic　immunosensing　platform　for　accurate　and　sensitive　detection　of　carcinoembryonic　antigen　(CEA)　based　on　Ag-doped/Pd　nanoparticles　loaded　MoO3　nanorods　(Ag/MoO3–Pd).　Initially,　the　presence　of　analyte　CEA　would　prompt　the　formation　of　sandwich-type　immunoreaction,　accompanied　by　the　introduction　of　Pt　NPs　labeled　on　detection　antibody.　Upon　the　addition　of　NH3BH3,　the　product　hydrogen　(H2)　will　interact　with　Ag/MoO3–Pd　as　a　bridge　between　the　sensing　interface　and　the　biological　assembly　platform.　Both　photocurrent　and　temperature　signals　can　serve　as　readouts　due　to　the　significantly　increased　PEC　performance　and　enhanced　photothermal　conversion　capability　of　H–Ag/MoO3–Pd　(the　product　of　Ag/MoO3–Pd　react　with　H2)　compared　to　Ag/MoO3–Pd.　In　addition,　the　DFT　results　show　that　the　band　gap　of　Ag/MoO3–Pd　becomes　narrower　after　the　reaction　with　H2,　thus　improving　the　utilization　of　light,　which　theoretically　explains　the　internal　mechanism　of　gas　sensing　reaction.　Under　optimal　conditions,　the　designed　immunosensing　platform　showed　good　sensitivity　for　CEA　detection　with　the　limit　of　detection　(LOD)　of　26　pg　mL−1　(photoelectrochemical　mode)　and　98　pg　mL−1　(photothermal　mode).　This　work　not　only　presents　the　possible　reaction　mechanism　of　Ag/MoO3–Pd　and　H2,　but　also　creatively　applicate　it　in　photothermal　biosensors　that　give　a　new　path　for　devising　dual-readout　immunosensor.　©　2023　Elsevier　B.V.