Guelleh was born in Dire Dawa, Ethiopia, into the politically powerful Mamassan subclan of the Dir Issa clan. The father of Ismaïl Omar Guelleh, son of Guelleh Batal, is Omar Guelleh, one of the first native teachers in the 1930s before working, following his father’s path, on behalf of the Franco-Ethiopian Railway Company (CFE) which built the line connecting Djibouti to Addis Ababa and whose head office was in Dire Dawa. When Guelleh was younger he attended a traditional Islamic school. In the 1960, Guelleh migrated to Djibouti before finishing high school. In 1964, at the age of 18, Ismail Omar Guelleh began working in the General Information of the French Territory of the Afars and the Issas, because he spoke Amharic, Somali, Arabic, French, Italian and English.

In 1974, he was suspended from his duties because he was suspected of transmitting information to the independence movement. He then became involved in the African People’s League for Independence (LPAI) chaired by Hassan Gouled Aptidon, who campaigns for independence. After Djibouti became independent, he became head of the secret police and chief of the cabinet in the government of his uncle Hassan Gouled Aptidon. He received training from the Somali National Security Service and then from the French Secret Service, and was intended to become his uncle’s successor.

Guelleh was first elected as President in 1999 as the handpicked successor to his uncle, Hassan Gouled Aptidon, who had ruled Djibouti since independence in 1977. Guelleh was re-elected in 2005, 2011 and again in 2016; the 2011 election was largely boycotted by the opposition amid complaints over widespread irregularities. Guelleh has been characterized as a dictator, and his rule has been criticized by some human rights groups.

On February 4, 1999, President Gouled Aptidon announced that he would retire at the time of the next election, and an extraordinary congress of his party, the ruling People’s Rally for Progress (RPP), chose Guelleh as its presidential candidate. As the joint candidate of the RPP and moderate wing of the Front for the Restoration of Unity and Democracy (FRUD), Guelleh won the presidential election held on April 9, 1999 with 74.02% of the vote, defeating his only challenger, the independent candidate Moussa Ahmed Idriss. He took office on May 8. Moussa Ahmed Idriss was arrested the following September for “threatening the morale of the armed forces” and detained at an undisclosed location.

In December 2000, Guelleh sacked the chief of staff of the National Police Force, Yacin Yabeh; policemen loyal to Yacin unsuccessfully rebelled following his dismissal.

Guelleh was nominated by the RPP as its presidential candidate for a second time on October 7, 2004, at an Extraordinary Congress of the party. He was backed by several other parties and was the only candidate in the presidential election held on April 8, 2005. Without a challenger, he won 100% of the ballots cast and was sworn in for a second six-year term, which he said would be his last, on May 7.

However, in 2010, Guelleh persuaded the National Assembly of Djibouti to amend the nation’s Constitution, allowing him to stand for a third term. This cleared the way for him to place his name on the ballot in Djibouti’s 2011 election. It also resulted in large protests beginning in 2010 similar to the larger movement for democracy in the Arab countries. The protests were quickly put down.

He was awarded with the Padma Vibhushan, India’s second highest civilian award on 25 January 2019 for his role in the safe evacuation of Indian citizens from Yemen.