It was Mr Maskey's first engagement in office and as he arrived, he was heckled by a lone protester.
Mr Maskey said he intended to continue reaching out to all sections of the community.
"I have said that I will do my best to be representative of all the citizens of Belfast.
"I am delighted to be able to take up this opportunity and it will continue throughout my year in office," he said.
The outgoing Presbyterian Moderator, Dr Alastair Dunlop, said he would welcome anyone who comes to the opening of the assembly.
"The first citizen of Belfast, although he is Sinn Fein and not many Presbyterians would necessarily vote for his party, nonetheless I think it is right and proper, in a Christian setting, that we should welcome the chief citizen of Belfast and that we should worship in a way that glorifies God."
Dr Russell Birney, the incoming moderator, said it was good that the new lord mayor attended the opening.
"He knows exactly what he's coming to and, as the moderator has already said, we have been working consistently for the day when we can dialogue with each other, when we can talk with all people and I think Alex Maskey is taking a risk as well," said Dr Birney.