"We showed that we could decide our own future," Zatlers said at the Freedom Monument, in the centre of Riga.
More than a quarter of the total population of seven million people participated in the peaceful protest and act of solidarity on August 23, 1989.
Soviet rule over the Baltic nations was secretly decided in a pact between Stalinist Moscow and Nazi Germany in 1940.
The deal was precipitated by the Molotov-Ribbentrop Pact between Berlin and Moscow, a non-aggression pact that was signed days before the commencement of the Second World War.
That saw Poland carved up between the two nations in 1939 and the Baltic countries later handed to the Soviets.
Many Russian historians have said that pacts were crucial as they mark occasions when the West failed to stand up to Nazi expansion.
"We must remember that, 70 years ago, the leaders of other countries cynically decided our fates," Zatlers said Sunday.
Russia had previously ruled the Baltic states until the First World War.
Following the Baltic Way, protests continued regardless of crackdowns in Latvia and Lithuania in January 1991.
The Baltic nations gained independence after a failed coup against a reformist Russian government in August 1991 speeded-up the Soviet Union's collapse.