The party's 482-seat haul was roughly in line with the number it held in the outgoing parliament.
Turnout at the five-yearly elections for members of the parliament and local councils exceeded 99 per cent, authorities have said, in line with past elections.
The unicameral parliament has virtually no power to challenge the party's key decisions, including on personnel, but it has occasionally amended proposed laws.
The National Assembly is scheduled to hold its first weeks-long session from April 6.
During that plenary, lawmakers will confirm new state leaders to be named by the party, including the prime minister and the president.
To Lam, who was confirmed as general secretary at the party's January congress, is widely expected to be chosen as president as well.
Lam's expected elevation would further align Vietnam's political structure with that of neighbouring China, where Xi Jinping also serves as general secretary of the Chinese Communist Party and president.
Vietnam and China are among a handful of communist-ruled states in the world.
Although the two neighbours have a long history of mistrust and territorial disputes, including over islands and waters in the South China Sea, their Communist parties remain officially close.
The conclusion of the election comes as Vietnam grapples with the spillover effects of the deepening Middle East crisis on global trade, energy markets and regional stability.
