Searching for the production of Higgs boson in association with a pair of top quarks would allow a direct measurement of the top quark Yukawa coupling and will provide an important test of the Higgs mechanism within the Standard Model. A search for this process is presented using proton- proton collisions at sqrt(s) = 13 TeV, collected by the ATLAS detector in both 2015 and 2016. Higgs boson decaying to two b quarks, and top pair decaying in semi-leptonic or dileptonic are considered.