Designing　new　biochemical　sensors　and　achieving　selectivity　and　high-sensitivity　analysis　is　one　of　main　research　directions　for　immunoassays.　Herein,　a　liposome-amplification　photoelectrochemical　(PEC)　immunoassay　was　developed　using　ultrathin　mesoporous　bismuth　chloride　oxide　nanosheets　(BiOCl　MSCN)　for　the　highly　selective　and　sensitive　detection　of　carcinoembryonic　antigen　(CEA).　Based　on　good　photocurrent　response　of　BiOCl　MSCN　toward　dopamine,　a　liposome-conjugated　secondary　antibody　loaded　with　dopamine　was　added　for　specific　recognition　in　the　presence　of　CEA.　After　the　lysis　treatment,　the　liberated　dopamine　was　injected　into　the　three-electrode　electrolytic　cell　to　enhance　the　photocurrent　of　BiOCl　MSCN.　Under　the　optimized　conditions,　the　constructed　liposome-mediated　PEC　immunoassay　showed　high　sensitivity　against　CEA,　with　a　dynamic　response　in　the　linear　range　of　0.05　ng　mL−1　to　100　ng　mL−1　and　a　detection　limit　of　35　pg　mL−1.　The　present　study　proposes　a　new　approach　to　the　liposome-mediated　PEC　immunoassay　constructed　on　ultrathin　mesoporous　BiOCl　nanosheets,　which　can　be　used　to　target　further　the　study　of　the　sensing　mechanism.　©　2023　Elsevier　B.V.