From Tuesday, the zone will expand to cover the whole of Greater London, meaning drivers of older vehicles in outer London boroughs will be hit with a £12.50 daily charge.
Car horns hooted in response to the Beep For Freedom banners that were held by members of a crowd gathered outside Tooting Broadway station.
Protesters chanted “Get Khan Out" while holding signs opposing the scheme’s expansion.
Among those opposing the scheme, which is being brought in by London mayor Sadiq Khan, was retired financial planner Warren Stephens, 50, who suggested it is “all about money and control".
Speaking to the PA news agency, Mr Stephens, whose car is Ulez compliant, said: “It is saying you are ‘OK to drive your polluting car if you give me £12.50’.
“It is all about money, otherwise they would ban petrol and polluting cars."
Pete Huntingford, 57, a DJ and scrap metal dealer from Mitcham, said he was “annoyed" about the Ulez scheme because he fears it could hurt people’s working and social lives.
He said: “It will mean I will not be able to go to work in certain areas, or go shopping where I want to, or to take my kids to certain areas.
“It will mean I am just being pushed out of the areas that I want to be.”
An airport worker, who only gave his name as Nick B, joined the demonstration after seeing a Ulez camera go up in his street in Selsdon, a minute’s drive from the restriction zone.
The 42-year-old shift worker said: “Just seeing it there, (made me feel) it is invasive.
“My car is Ulez-compliant but a lot of my neighbours cars are non-compliant.
“You drive for your shopping to the nearest supermarket and to go about 150m down the road will now cost £12.50.
“It is the same as if you have driven from one side of London to the other and it makes no sense."
TfL has introduced a £160m scrappage scheme for residents, small businesses, sole traders and charities to claim grants.
Mr Khan has previously said that clean air is “a human right, not a privilege" and he is “listening" to people’s concerns about the scheme.
On Saturday the GMB Union called on Mr Khan to scrap Ulez expansion.
GMB London regional organiser Trevlyn McLeod told LBC: "Listen to the people, Mr Khan, listen to the people who are going to suffer, listen to the people who can’t afford now to go to work or never mind put food on the table"
"We all want clean air for our children and generations, but you’ve gone in too far, too deep and it’s going to cost people’s lives and livelihoods."
A mayoral spokesperson said: “The mayor has always been clear that the decision to expand the Ulez was a very difficult one, but he is not prepared to stand by while around 4,000 Londoners die prematurely each year due to air pollution."