This paper reports on a search for narrow resonances in diboson production in the $$\mathrm {\ell \ell }q\bar{q}$$ final state using $$pp$$ collision data corresponding to an integrated luminosity of $$20$$ fb $$^{-1}$$ collected at $$\sqrt{s}=8$$ TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 % confidence level are set on the production cross section times branching ratio for Kaluza–Klein gravitons predicted by the Randall–Sundrum model and for Extended Gauge Model $$W^\prime $$ bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and $$W^\prime $$ boson respectively.