Boim was the principal of the Rogozin comprehensive High School in Kiryat Gat.
He served as mayor of Kiryat Gat, as well as Chairman of the Municipal Environmental Quality Association of Ashkelon District; Chairman of the Board of Directors of the Economic Company of Kiryat Gat; and Chairman of the Directorate of the Inter Regional Industrial Park of Kiryat Gat and Hevel Lakhish.
In 1996, Boim was elected to the Knesset on the Likud list, serving as the party's whip, head of the Negev Lobby, and head of the Knesset Delegation to the Annual Dialogue between Israel and the European Parliament during his first term. After being re-elected in 1999, he served as coalition and Likud faction chairman.
He was re-elected again in 2003 and served as Deputy Minister of Defense from March 2003 until January 2006. In 2005 he defected to the new Kadima party while still retaining his ministerial position. In January 2006 he became Minister of Housing and Construction and Minister of Agriculture and Rural Development, serving in both positions until May. He was re-elected in 2006, and was then appointed Minister of Immigrant Absorption, before returning to the Housing and Construction portfolio in 2007. Placed sixth on Kadima's list, he retained his seat in the 2009 elections.
In 2004, responding to a question about terrorism and Islamic political violence, Boim remarked: "What is it about Islam as a whole and the Palestinians in particular? Is it some form of cultural deprivation? Is it some genetic defect? There is something that defies explanation in this continued murderousness." He was criticized for this statement by many members of the government, among them Meimad leader MK Rabbi Michael Melchior, who said that Boim's comment was racist and against the tenets of Judaism. He later apologized for his remarks, saying he was speaking after a recent Palestinian attack and was overwhelmed by the scope of the bloodshed at the time.