Arad returned to Israel in 1975 and was offered positions with the Mossad and with the Ministry of Foreign Affairs. He chose to join the Mossad, where he spent most of his professional career. He served in two divisions, one of which was the Research (Intelligence) Division, which he eventually headed (at the rank equivalent to Major General). At the Mossad, he also dealt with foreign liaison and his assignments also included posts abroad, acquiring the reputation, in the words of Andrew Marshall, the Director of the Pentagon's Office of Net Assessment, "a top global defence strategist".