Rhodri Morgan said he would listen to the people of Wales as he was nominated as the Welsh assembly's first minister.
Mr Morgan, who will lead a minority Labour government, said: "I am not the boss - the people are the boss".
He was speaking at the assembly at the end of a week when it appeared he would not return as first minister, until an opposition coalition fell through.
The assembly government confirmed later on Friday the Queen had appointed Mr Morgan following his nomination.
Returning for his third term as first minister, Mr Morgan had told AMs in Cardiff Bay he was "thrilled and hugely honoured" but his government would listen to the message that had come from the people of Wales.
"I know it won't be easy," he said.
"Minority governments can have all their legislative and budgetary proposals rejected.
"We will be seeking to build a progressive consensus and reach out to others of a like mind. They expect us to take Wales in the direction they voted for."
The Labour party won 26 of the 60 seats in the 3 May election, five short of a majority.
Labour AM Jane Hutt, who nominated Mr Morgan, said the people of Wales knew and admired Mr Morgan, and the Labour party sought to unite not divide.
Plaid Cymru leader Ieuan Wyn Jones - who would have become first minister if the opposition coalition had gone ahead - agreed the way forward would not be easy but the era of political plurality should be welcomed.
"I have learnt a great deal in the last few weeks. But the biggest lesson for all surely is this, people have to work together in the best interests of the people of Wales.
"It will call for leadership, maturity and a willingness of all sides to be less tribal in our approach."
In the three weeks since the election, all four parties in the assembly had been involved in coalition talks.
This week, talks broke down between the Conservatives, Plaid Cymru and the Lib Dems over a possible rainbow coalition.
Speaking to BBC Wales after the session, Mr Morgan added that the idea of a rainbow alliance between Plaid, the Tories and the Lib Dems had collapsed as people did not want Conservatives in charge of spending.
Conservative group leader Nick Bourne told AMs the election had been devastating for Labour and the Labour party had "seemed out of touch" in negotiations with the other parties.
And he warned that if Labour's promise of "progressive consensus" did not materialise a "viable alternative" would be in prospect "because the people of Wales deserve better than what they have had over the last eight years."
Lib Dem leader Mike German said the election showed there needed to changes at the heart of the decision-making process. "It is going to be a very challenging time for the first minister," he added.
Previously, Labour had held unsuccessful talks over forming a government with Plaid and the Lib Dems.
Plaid Cymru has 15 seats in the new assembly, the Conservatives 12 and Liberal Democrats six.