The 52-year-old former chartered surveyor spent the years of Indonesia's occupation of East Timor living in political exile, only returning to the territory in 1999 ahead of the vote for independence.
He was engaged in academic teaching in Mozambique, and told the Asia Times last year: "I haven't been seeking a career as a prime minister, and I hope to return to academic life in the future."
Political animal
But he established his political roots from an early age.
He entered political life in January 1970, when he was 20, with the establishment of the Movement for the Liberation of East Timor when the territory was still under Portuguese rule.
Mr Alkatiri went on to become one of the founder members of Fretilin, the party which was instrumental in achieving East Timor's independence from Indonesian rule.
The descendant of Yemeni settlers, his brother is the leader of Dili's Islamic community - a minority in the predominantly Catholic country - and Mari Alkatiri himself is a practising Muslim.
He is married to fellow-Timorese Marina Ribeiro and they have three children.
'Tough negotiator'
When East Timor finally voted to become independent he entered the interim administration as economics minister, forging his reputation as a tough operator as chief negotiator over the rich petroleum resources in the sea between Australia and Timor.
While Mr Alkatiri has remained loyal to the party he helped set up, Mr Gusmao has since split with Fretilin and complained that it conducted a whispering campaign against him in the run-up to the presidential election.
Mr Alkatiri said at the time of the territory's presidential poll that he would not be voting for the man he will now help run the half-island's new government.
He told reporters before the election in April that his priority would be to go to the beach, and that he would be casting a blank vote.
Tensions
The two men are reported to disagree over a number of issues - not least, over the fate of former militia members who perpetrated horrific violence after East Timor voted, three years ago, to become independent.
But nevertheless they are intent on presenting an image of national unity in the run-up to East Timor's independence.
Mr Alkatiri publicly welcomed Mr Gusmao's victory in the election.
"I have come here to congratulate Xanana Gusmao. I do this from the bottom of my heart, believe it or not," he told reporters.