Htin Kyaw, a close confidante of Suu Kyi, took power Wednesday from the outgoing quasi-civilian government led by former general Thein Sein.
The Southeast Asian nation is in the throes of a dramatic transformation as it emerges from the shadow of a military dictatorship and moves to open its economy to global markets.
"I have the obligation to work toward achieving a constitution that has democratic norms and is suitable for the nation," Kyaw said in his speech.
"I want to tell the new government, we must constantly try to fulfill the hope and will of the people of this country," he added.
Suu Kyi - a former dissident and leader of the National League for Democracy - is barred from becoming president by the constitution. But she has vowed she will steer the government anyway, taking on cabinet positions.
Still, a key challenge for Suu Kyi's administration will be maintaining smooth relations with a military that locked her and many of her colleagues up for years under the junta.
A state in transition
Myanmar has been under military or military-dominated rule since a 1962 coup. Elections last November that brought the new government to power were the first openly contested polls since 1990.
Two vice presidents, one of them a military nominee, are also due to take the oath of office. Several key posts in the government, including defense, will be reserved for the military. A quarter of the parliament is also reserved for military appointees.
The country's challenges are immense. Civil wars continue to rage in tribal borderlands, poverty is widespread and the military continues to hold huge political and economic clout.