Suu Kyi, whose unswerving campaigning saw her locked up for years by the former junta and earned her a Nobel Peace Prize, appeared calm as she arrived to take her seat as an elected politician for the first time in the capital Naypyidaw.
"I will try my best for the country," she told AFP.
The democracy champion's first taste of public office comes at an uncertain time for Myanmar after recent communal violence and a series of student arrests cast a shadow over promising changes in the former pariah state.
But it also comes amid expectations that several senior hardliners are to be replaced by reformists in an imminent cabinet reshuffle that would mark the first major change of personnel in the top echelons of government since it replaced junta rule last year.
Suu Kyi will join fellow members of her National League for Democracy (NLD), as both the party and its charismatic leader transform from dissident outsiders to mainstream political players in the wake of landmark April by-elections.
The 67-year-old, one of the NLD's 37 lower house members of parliament, postponed her debut in the fledgling legislature last week to recover from a gruelling European tour and visit her constituency.
Fellow lower house NLD MP May Win Myint said she was "excited" about Suu Kyi's arrival.
"We are ready to support her," she said.
Parliament is still dominated by the military and its political allies, but even military men appeared pleased to see the veteran activist, despite NLD plans to ease them out of the legislature by scrapping a constitutional provision granting them a quarter of seats.
"It's good that she arrived today, we all welcome her," said Brigadier General Wai Lin.
No special provisions were made for the attendance of Myanmar's most famous political figure, who listened attentively as other MPs spoke in a morning debate.
Suu Kyi barely created a stir among legislators in the lower house, but was surrounded by members of the press during a coffee break, telling reporters she had yet to decide on any proposals to submit to the parliament.
MPs have a number of pressing issues on the table for discussion during the current session, which began last Wednesday.
Communal violence in June between ethnic Buddhist Rakhine and Muslim Rohingya, which left dozens dead and tens of thousands homeless, is on the agenda, with an ongoing state of emergency requiring parliamentary approval.
A new foreign investment law aimed at resuscitating the country's moribund economy is also in the pipeline.
Suu Kyi on Tuesday pledged her party would join "the legislative concert" and push for greater transparency once inside parliament.
The party's involvement in mainstream politics comes as a result of sweeping changes by a new regime, including the release of hundreds of political prisoners, liberalising sections of the battered economy and tentative ceasefires with several major armed ethnic rebel groups.
But the government came under fire from other activists last week after authorities on Friday briefly detained around 20 student leaders ahead of the 50th anniversary of a brutal suppression of a student protest.
They were freed late Saturday.