The number of lawmakers, if confirmed, would be too small to form a parliamentary group which would give the FN a role in setting the agenda and win positions on committees. The party will have far more than the 289 seats needed for an absolute majority to carry out Macron's program.
German Chancellor Angela Merkel was among the first to congratulate Macron.
Germany and France have the eurozone's two biggest economies and are the traditional motor of European integration.
France's youngest leader since Napoleon, Mr Macron emerged from relative obscurity to score a thumping win in the presidential election in May.
Foreign Minister Sigmar Gabriel also welcomed the vote's outcome, tweeting that it paved "the way for reforms in France+Europe".
"We should not claim victory because we suffered quite a blow", said Collard, who won his seat by a mere 123 votes.
Macron left a position in the Socialist government to run an independent presidential campaign.
Polls before the vote showed Macron on course to win the biggest parliamentary majority since de Gaulle's own conservatives in 1968.
"A year ago, no-one would have imagined such a political renewal", Prime Minister Edouard Philippe said.
Workers unions have already criticized the labor reform and the president's decision to skirt normal procedure to pass changes that would short-circuit extended debate and nix amendments.
"We are the only force that will fight against the dilution of France", Le Pen said in a televised statement, declaring victory. Experts partly blamed voter fatigue following the May election of Mr Macron, plus voter disappointment with politics.
Le Pen entered parliament for the first time in her career in one of at least eight seats the FN won, but the party was set to fall well short of its 15-seat target. He said conservative lawmakers are going to have a strong bloc in the lower house to be able to voice their views.
This is the very first legislative election for En Marche, but now that his party has a majority in the Assembly. The Front National, though recently so close to the country's highest office, held 10%, still defeating the socialists ambysmal 6%.
Many candidates in his party joined only after Macron won the presidency in May.
One of the challenges for Macron as he sets out to overhaul labour rules, cut tens of thousands of public sector jobs and invest billions of public cash in areas including job training and renewable energy, will be to keep such a diverse and politically raw group of lawmakers united behind him.
Voter turnout was projected to be a record low at about 42 per cent.
A fierce nationalist, Le Pen stuck during the presidential run-off race to promises to exit the euro currency, long at the heart of her economic platform, even though most French citizens and some of her top allies like Collard oppose the move.
Nevertheless, the anti-establishment party fared better than pollsters forecast over the past few days and has a greater presence in parliament than the past five years, when it had only two MPs. At 5 p.m. local time, it was 35.33 percent compared with 46.42 percent in 2012 and 49.58 percent in 2007, according to the Interior Ministry in a post on Twitter.
Curious crowds gathered in the northern seaside town of Le Touquet where Macron cast a ballot Sunday morning in the second round of elections for the 577-seat National Assembly.
Far-left leader Jean-Luc Melenchon, who will be another formidable opponent in the parliament after winning a seat from the southern port of Marseille, said voters had gone on "civic general strike" by not voting in the parliamentary polls.