Herein,　an　in　situ　amplified　photoelectrochemical　(PEC)　immunoassay　with　ZnO　microflowers　(ZnO　MFs)　decorated　with　gold　nanoparticles　(Au　NPs)　was　developed　to　determine　human　prostate-specific　antigen　(PSA)　using　l-cysteine-loaded　liposomes　for　signal　amplification.　Initially,　ZnO　MFs　with　smooth　and　well-defined　morphology　were　synthesized　under　hydrothermal　conditions.　The　heterostructured　microflowers　were　formed　by　depositing　Au　NPs　on　ZnO　microflowers　using　trisodium　citrate.　l-Cysteine　(l-Cys)-encapsulated　liposomes　conjugated　with　detection　antibodies　were　used　to　fabricate　a　sandwiched　immunocomplex　on　a　capture　antibody-modified　microtiter　plate　in　the　presence　of　target　PSA.　The　liposomes　were　lysed　using　Triton　X-100　to　release　the　encapsulated　l-Cys,　thereby　increasing　the　photocurrent　on　Au　NP-decorated　ZnO　MFs.　Results　indicated　that　the　photoelectrochemical　immunoassay　displayed　good　photocurrents　to　response　PSA　concentrations　from　0.01　to　20　ng　mL-1,　and　the　detection　PSA　concentration　was　as　low　as　0.79　pg　mL-1.　Furthermore,　the　photoelectrochemical　immunoassay　had　good　precision,　high　selectivity,　and　well-matched　accuracy　toward　target　PSA　in　human　serum　specimens　using　the　commercialized　human　PSA　ELISA　kit　as　a　reference.　©　2021　American　Chemical　Society.