This document presents the recent results of the ATLAS experiment at the LHC concerning the t ¯t resonance and vector-like quark searches. A search for t ¯t resonances at 13 TeV in protonproton collisions data is performed in the lepton+jet final state and for boosted top topologies. A re-interpretation of the analysis performed with the data recorded at the center of mass energy of 8 TeV, is also presented, for a scalar resonant signal. A vector-like top pair production is also searched for, through three analyses where the vector-like quark decay to Zt, Ht or Wb. A comparison of those analyses is presented. In addition, vector-like quarks are searched via the same sign lepton topology. The results are presented as mass limits on the vector-like top branching ratio plane and as the cross section limit on the T5=3 pair production.