The status of the search to produce a Higgs boson in association with a single top quark (tH) in multilepton final states is presented. The study uses an integrated luminosity of 139 fb-1 of LHC collision data at centre-of-mass-energy of 13 TeV, recorded by the ATLAS experiment. Two final states are studied in this work: three leptons (3l) and two leptons same-sign (2lSS) where only electrons and muons are considered. As for today, this is the only analysis sensitive to both the magnitude and the sign of the Yukawa coupling (yt) of the Higgs boson to the top quark and the first direct search of tH production in the ATLAS collaboration. The tH process has an extremely low production cross-section (70 fb at √𝑠 = 13 TeV), which originates from the destructive interaction of the diagrams where the Higgs couples to the top quark with those where the Higgs couples to the W boson. Other SM processes giving rise to similar final states and conforming the main background of this search, have production cross-sections up to seven times higher than that of tH. This fact makes multivariate analysis methods a key tool to distinguish signal events from the diverse large backgrounds. All these features make this search very challenging and this process exceptionally sensitive to deviations from SM predictions.