Cancer immunotherapy using tumor-specific monoclonal antibodies presents a novel approach for cancer treatment. A monoclonal antibody TA99 specific for gp75 antigen of melanoma initiates neutrophil recruitment in tumor responsible for cancer therapy. Here, a strategy is reported for hijacking neutrophils in vivo using nanoparticles (NPs) to deliver therapeutics into tumor. In a mouse model of melanoma, it is shown that systemically delivered albumin NPs increase in tumor when TA99 antibody is injected; and the NP tumor accumulation is mediated by neutrophils. After the administration of pyropheophorbide-a loaded albumin NPs and TA99, photodynamic therapy significantly suppresses the tumor growth and increases mouse survival compared with treatment with the NPs or TA99. The study reveals a new avenue to treat cancer by NP hitchhiking of immune systems to enhance delivery of therapeutics into tumor sites.