Galant began his military career in 1977 as a naval commando in the 13th Flotilla. In the 1980s, after six years in the flotilla, he moved to Alaska and worked as a lumberjack. He then returned to the navy and served on a missile boat (including a position as deputy-commander of INS Keshet) and again in the 13th Flotilla. In 1992, Galant was earmarked by then-navy commander Ami Ayalon for the command of the 13th Flotilla, a position he was meant to take up in 1994. Galant preferred not to study during the two remaining years, and instead moved into the ground forces and in 1993 took up command of the Menashe (Jenin) Brigade of the West Bank Division.
After serving for three years as commander of the 13th Flotilla, Galant moved up to command the Gaza Division. He also commanded the reserve 340th Armored Division (Idan Formation), and in 2001 became the Chief of Staff of the GOC Army Headquarters. Galant attained the rank of a major general when he became the Military Secretary of the Prime Minister in 2002. In 2005, Galant was appointed as commander of the Southern Command. During his tenure (that lasted until 21 October 2010), the Israel Defense Forces embarked on Operation Cast Lead against Hamas in the Gaza Strip. Galant commanded the operation and his role in the field and in the success of the operation gained praise and helped him in the race to Chief of Staff.
The Israeli NGO, Yesh Gvul, filed suit against Galant's appointment as IDF chief of staff, claiming that his command role in Cast Lead confirmed him as a suspect in "grave violations of international law."Haaretz noted that Galant lobbied against an investigation of Col. Ilan Malka, the IDF commander who approved the airstrike that killed 21 members of the al-Samouni clan during Cast Lead. Galant's view was ignored as the military prosecutor general opened an investigation of the incident which was highlighted by the Goldstone Report (since disavowed by its author) as a possible serious breach of international law.
On 22 August 2010, Minister of Defense Ehud Barak presented the candidacy of Galant for the post of the IDF's twentieth Chief of Staff to the government. It was expected that he would receive the promotion. Galant's appointment followed a controversy, where a forged document was transferred to Israel's Channel 2 which accused Galant of attempting to smear rival candidate Benny Gantz.
On 5 September 2010, the government approved the nomination of Yoav Galant as the next Chief of Staff, with only Likud minister Michael Eitan objecting. Prime Minister Benjamin Netanyahu said that the incoming IDF chief has "proven his worth during his 33 years of military service at the IDF's frontlines," and that "He's proven himself to be a courageous fighter, an excellent officer, and a responsible and serious battle commander." The PM added that Galant picked up on a legacy of "dedication and excellence" bequeathed by incumbent IDF chief Gabi Ashkenazi. The cabinet also approved Barak's proposal, according to which Galant would serve for three years, giving the defense minister power to grant a fourth.
On 1 February 2011, Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barak canceled the appointment of Galant to the post of Israel Defense Forces chief. The announcement came after months of scandal surrounding his appointment due to allegations that he had seized public lands near his home in Moshav Amikam. After conducting an investigation into the allegations, Attorney GeneralYehuda Weinstein said that his findings "raise significant legal difficulties for the decision to appoint him." Weinstein said that it was up to the prime minister and defense minister to decide whether or not Galant could take up the post as new IDF chief of staff. Earlier in the day, Weinstein notified Prime Minister Benjamin Netanyahu that he could not defend Galant's appointment as chief of staff due to legal impediments.
On 30 December 2012, the local planning committee administrating land ownership issues and building licenses said that Galant had built his home in the northern community of Amikam on 350m² of property accidentally listed as his, unaware that it was actually public land. The decision didn't address two other issues still being investigated by the state comptroller and attorney general: the building of an unauthorized access road to his house and the planting of an olive grove that spilled over the boundaries of his property.
In January 2015 Galant joined the new Kulanu party. He was placed second on the party's list for the 2015 elections, and was elected to the Knesset as the party won ten seats. He was later appointed Minister of Construction in the new government.