Ms Le Pen, who fought him for the presidency, won a seat representing her northern bastion around Henin-Beaumont with more than 58% of the vote.
Macron left a position in the Socialist government to run an independent presidential campaign.
"Through this vote, the French people have showed they preferred hope to anger, optimism to pessimism, confidence to closing in on oneself", Prime Minister Edouard Philippe said.
According to BBC correspondents, opponents of Macron may simply have not bothered to turn out. He said his determination is "total" to work on major reforms in the coming months.
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.
Macron's centrist Republic on the Move party, known as En Marche!
The president of the Republic has all the powers'.
While fans often compare his style to that of American presidents, he appears to be more inspired by Francois Mitterrand and Charles de Gaulle, two French leaders remembered for their monarchical style. He said lawmakers in his conservative party are going to have a strong enough bloc in the lower house of parliament to be able to voice their views. The Interior Ministry counted the Republicans and allied candidates with 131 seats, with 33 seats still uncounted.
Partial official results from France's second-round parliamentary elections show President Emmanuel Macron's centrist party with a clear lead over the country's traditional right-wing and leftist parties. The ministry said the far-right National Front was in third place with almost 10 percent followed by the Socialists with 6.2 percent.
Macron's party has 513 candidates vying for 573 seats. With its allies, it could get fewer than 50 seats, according to projections.
But turnout was estimated to be extremely low, at around 44 percent, giving his critics grounds to claim he has no groundswell of support.
The Socialist Party, which ruled France until last month, and its allies are projected to win 20 to 30 seats less than its current 277.
It has been a bad night for the Socialists, who are predicted to win just 27 to 49 seats - losing hundreds of their lawmakers.
At 43.4%, turnout was the lowest ever, seven percentage points less than in the first round and 10 percentage points less than the previous record low. At the end of the afternoon, turnout stood at only 35 percent - below last week's record low.
French voters have given President Emmanuel Macron's party a solid victory in the parliamentary election. We have won!, Le Pen said, "Voters of the 11th district elected me by nearly 58 percent and 66 percent for the town of Henin-Beaumont".
Le Pen's nemesis, the ultra-left Jean-Luc Melenchon, vowed a "social coup d'etat", saying Macron's plans to reform labor laws amount to "destruction of the social order".
Having never held elected office, he seized upon the growing resentment towards a political elite perceived as out of touch, and on public frustration at their failure to create jobs and spur stronger growth to win the Elysee.