Banging drums and waving banners that read "No to the IMF", marchers converged on the central Plaza de Mayo in front of the Casa Rosada presidential palace.
Macri's center-right government secured a three-year, USD 50 billion, IMF loan agreement in June to confront a currency crisis that has seen Argentina's peso lose half its value against the dollar this year.
Analysts say the government wants to gain more flexibility to access funds sooner than expected as well as increase the amount available to ease investor concerns.
An IMF spokesman said a budget proposal submitted by Macri's government was a key element in the reforms needed for a new loan package while adding that there was still no timeframe for finalizing the aid.
Macri, who is in New York to attend this week's UN General Assembly, said he was trying to restore economic confidence.
"We are working with the IMF team and we will present something that will bring confidence, more confidence than what we have had in the last 10 days when markets have turned around and things are moving better," he said.
"There is no chance that Argentina will default," he added at an event hosted by Bloomberg television in New York.
"It is a very clear monetary policy that will show where we are going, that will show that we are really going to drop dramatically down the inflation and our needs for financial external support."
On the streets of Buenos Aires, teachers' union member Sonia Alessio said: "We are against the adjustment of Macri, against the adjustment of the IMF, particularly as teachers are fighting for more budget funds for education."
Some public services, like schools, hospitals, and public administration offices, had already shut down ahead of Tuesday's general strike.
Public transport is expected to grind to a halt, banks will remain shut and air traffic controllers will suspend activity.
Airlines were working to reschedule flights.
Production and Labour Minister Dante Sica regretted the timing of the strike, saying Argentina was in a period "when economic activity is still falling and we have to start recovering it". He told reporters the government would "keep open channels for dialogue" with the unions.