Minor scuffles broke out between police and protesters, some of whom played drums and horns and set off flares and smoke bombs, while chanting against cuts to social welfare programs.
The protest crippled traffic in the heart of the Belgian capital as well as major roads, choking off transportation hubs.
Belgium's three major trade unions organised the protest and country-wide strikes against cuts to the pension and healthcare systems proposed by De Wever, who had vowed to slash spending to try and overcome the country's economic challenges.
Organisers estimated more than 150,000 joined the demonstration while the police put the crowd at 80,000.
A general strike grounded most airplanes at the country's two main airports.
All flights due to depart from Brussels International Airport and about half of those scheduled to land were cancelled as staff from the security firm providing X-ray screening walked out on Tuesday, a spokesperson for the airport said.
The Federal Planning Office of Belgium expects Belgium's already steep budget deficit to rise to 6.5 per cent of GDP by 2030.
De Wever, who took office in February, has pledged to reduce deficits without raising taxes but is facing challenges in finalising next year's budget.
with Reuters
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