The anti-establishment camp, including pan-democrats and localists, won 30 of the legislature's 70 seats, while the pro-establishment camp took 40 seats, down from the 43 they won in the 2012 election, according to the final election results released Monday.
Helped by a record voter turnout, some of the young protesters who took part in Hong Kong's enormous 2014 pro-democracy demonstrations will now wield a small measure of real political power for the first time.
"I think. the result of the election is the indicator to show whether Hong Kong people accept independence as our future or not".
The victory of at least four young candidates including Nathan Law, 23, who led mass "democracy rallies" two years ago, is likely to strain ties with China's Communist Party.
Secondary school students pushing for Hong Kong's breakaway from China have threatened protests after staff stopped them from handing out political pamphlets, as the government puts pressure on independence activists. One of them, Yau Wai-ching of new party Youngspiration, gained a seat saying Hong Kong had "the right to discuss its sovereignty".
His constituency will elect six seats and he was now in second place, with 90 per cent of votes counted, the results showed.
Hong Kongers have sent several young, radical politicians into the city's legislature in a landmark election that could lead to increased tensions between the city and the Beijing government.
Full results were due out later in the day.
There will also be more radical voices in the LegCo, with at least six young candidates who support self-determination for Hong Kong occupying seats.
Before nomination for the election, Hong Kong's Electoral Affairs Commission demanded that all the candidates must endorse a statement promising to support the Hong Kong Basic Law and be loyal to the Hong Kong SAR.
The LegCo has 70 constituency seats but only 35 of these are elected directly by Hong Kong's population. "Pan-democrat" lawmakers now control 27 of 70 seats, compared with 43 held by lawmakers friendly to Beijing.
Pro-Beijing supporters have been accused of offering financial incentives to potential supporters and bringing in busloads of former Hong Kong residents living in China to vote in the election.
Voters flocked to cast ballots in record numbers with some having to wait several hours after the close of polling to cast ballots at a few particularly congested polling stations.
Those protests posed one of the greatest challenges to Beijing's rule in decades and were deemed illegal by the local government in Hong Kong and the central government in Beijing.
Lawmakers are supposed to start their mandate by swearing an oath to uphold the constitution, which describes Hong Kong as part of China.
It is nearly impossible for the democracy camp to take a majority in LegCo as 30 of its 70 seats are elected by special interest groups representing a range of businesses and social sectors.
That is about 6% of the population, who are overwhelmingly Beijing-leaning.
Britain in 1997 handed the city back to China under a "one country, two systems" agreement, with its rights and freedoms guaranteed for 50 years under a semi-autonomous system.