Objective:Thepredictiveandprognosticroleofprognosticnutritionalindex(PNI)ingastriccancerpatientswithperitonealdisseminationremainsunclear.ThisstudyaimstoexploretheroleofthePNIinpredictingoutcomesofgastriccancerpatientswithperitonealdissemination.Methods:Atotalof660patientsdiagnosedwithgastricadenocarcinomawithperitonealmetastasisbetweenJanuary2000andApril2014atSunYat-senUniversityCancerCenterandtheSixthAffiliatedHospitalofSunYatsenUniversitywereretrospectivelyanalyzed.Theclinicopathologiccharacteristicsandclinicaloutcomesofpatientswithperitonealdisseminationwereanalyzed.Results:ComparedwithPNI-highgroup,PNI-lowgroupwascorrelatedwithadvancedage(P=0.036),worseperformancestatus(P<0.001),higherfrequencyofascites(P<0.001)andhigherfrequencyofmultisitedistantmetastasis(P<0.001).Kaplan-MeiersurvivalcurvesshowedthatPNI-highgrouphadasignificantlylongermedianoverallsurvivalthanPNI-lowgroup(13.13vs.9.03months,P<0.001).MultivariatesurvivalanalysisrevealedthatBorrmanntypeIV(P=0.014),presenceofascites(P=0.017)andlowerPNI(P=0.041)wereindependentpoorprognosticfactors,andpalliativesurgery(P<0.001)andfirst-linechemotherapy(P<0.001)weregoodprognosticfactors.Forpatientsreceivingpalliativesurgery,thepostoperativemorbidityratesinthePNI-lowgroupandPNIhighgroupwere9.1%and9.9%,respectively(P=0.797).ThepostoperativemortalityratewasnotsignificantlydifferentbetweenPNI-lowandPNI-highgroups(2.3%vs.0.9%,P=0.362).Conclusions:PNIisausefulandpracticaltoolforevaluatingthenutritionalstatusofgastriccancerpatientswithperitonealdissemination,andisanindependentprognosticfactorforthesepatients.