pecies ofPhalarishave historically been controlled by acetyl-coenzyme A carboxylase(ACCase)-inhibiting herbicides; however, overreliance on herbicides with this mechanism of actionhas resulted in the selection of resistant biotypes. The resistance to ACCase-inhibiting herbicideswas characterized inPhalaris brachystachys,Phalaris minor,andPhalaris paradoxasamples collectedfrom winter wheat fields in northern Iran. Three resistant (R) biotypes, one of eachPhalarisspecies,presented high cross-resistance levels to diclofop-methyl, cycloxydim, and pinoxaden, which belongto the chemical families of aryloxyphenoxypropionates (FOPs), cyclohexanediones (DIMs), andphenylpyrazolines (DENs), respectively. The metabolism of14C-diclofop-methyl contributed to theresistance of theP. brachystachysR biotype, while no evidence of herbicide metabolism was found inP. minororP. paradoxa. ACCasein vitroassays showed that the target sites were very sensitive to FOP,DIM, and DEN herbicides in the S biotypes of the three species, while the RPhalarisspp. biotypespresented different levels of resistance to these herbicides. ACCase gene sequencing confirmedthat cross-resistance inPhalarisspecies was conferred by specific point mutations. Resistance in theP. brachystachysR biotype was due to target site and non-target-site resistance mechanisms, while inP. minorandP. paradoxa, only an altered target site was found.