Precise measurements of the properties of the top quark test the Standard Model (SM) and can be used to constrain new physics models. ATLAS collaboration performed a direct measurement of the decay width of the top quark using ttbar events in the lepton+jets and dilepton final states. The data sample was collected by the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 13 TeV and corresponds to an integrated luminosity of 140 fb−1. A multivariate technique is employed in the lepton+jets channel to resolve the ambiguity of the jet-to-parton assignment. The decay width of the top quark is extracted from the data using a profile likelihood method using the distributions of variables sensitive to the top-quark decay width in tt ̄ pair production.