Attendance was helped by good weather, and the usual parade of celebrants included the ambassadors of Russia, Kazakhstan and Belarus, Rīga mayor Nils Ušakovs and a selection of his Saskana party colleagues.
Known as "Victory Day" to some, May 9 remains a divisive date in Latvia. While many ethnic Russians, who make up around a quarter of the population, see it as a day of commemoration and celebration, most ethnic Latvians see it as the start of a second, harsh 50-year Soviet occupation.
The official Latvian day for commemoration of victory over the Third Reich is 'VE Day', May 8, with May 9 designated Europe Day and marked by smaller events on the other side of the River Daugava.
Caught between Russia and Germany, more than 100,000 Latvians fought on opposite sides during the second world war.
The event will conclude in the evening with a concert and a fireworks display.
The orange and black St George ribbon was worn by many attendees.
The Riga event is not a holiday in Latvia and has no official backing, though police are forced to organize a large operation each year to regulate traffic and maintain public order.
By the end of the day police said they had made 27 arrests for offenses including urinating in a public place, petty hooliganism, being in a public place under the influence of narcotic or psychotropic substances, being drunk in a public place and not complying with the instructions of police officers.