The demonstration began at 3.00 p.m. at Narinkkatori and ended at 5.00 p.m. in Senaatintori.
The TTIP agreement deals with investment and trade between the EU and the USA and is due to be completed at the end of the year.
The demonstrations called for the suspension of contract negotiations.
According to the NGOs that organised the march, the agreement has been prepared in an undemocratic manner.
They said the aim of the agreement is subordination of various sectors of society to the profits of big businesses.
