VJ Day on 15 August 1945 followed the destruction of Hiroshima and Nagasaki by atomic bombs.
On Saturday, services have been held at St John's Church in Cardiff and at the war memorial in Llandudno, Conwy.
A national service is taking place at Llandaff Cathedral on Sunday where First Minister Carwyn Jones will give a reading.
The Cardiff Branch of the Burma Star Association has held its service at St John's Church.
About 300 people joined the parade from Llandudno Pier Head to the war memorial where a drumhead service was placed.
Canon of Dr Sarah Rowland Jones, from St John's Church, said: "The Burma Star Association was set up in 1951, and ever since we've had the veterans coming and holding a service annually.
"They're now down to single figures, only a couple of them are hail and hearty in their mid-90s and so they decided the time had come on the 70th anniversary of VJ Day to lay up their standard.
"So what we are doing today is holding a service in which the standard will be paraded as usual but at the end of the service it will be handed over to the church's safe keeping and we shall we hanging it up permanently right next to the Burma Star window so that it can be there for future generations to look at and be prompted to remember."
The national service the following day, which is open to the public and has been organised by the Welsh government, Cardiff council and Llandaff Cathedral, will start at 15:30 BST.
Speaking ahead of the event Mr Jones said: "We must never forget the sacrifice allied forces made for our freedoms during World War Two.
"Victory in Japan by the allied forces brought to an end six years of conflict which saw the tragic loss of so many lives and the destruction of so many communities across the world.
"Their heroics in battle, often so very far from home, will always have a special place in our hearts and it's important we remember and show our gratitude for their service."

Ogier's win in the three-day road gravel event in New South Wales was his seventh of the season as the French driver beat Volkswagen Polo R team-mate Jari-Matti Latvala by 12.3 seconds.
The 31-year-old said: "It's an amazing season, the best I've ever done."
Ogier joins Sebastien Loeb (nine), Juha Kankkunen and Tommi Makinen (both four) in winning three or more world titles.
Volkswagen's 1-2 in Australia secured a third manufacturers' crown for the German team.
Ogier won the final seven speed tests to take victory in Australia, overhauling Northern Ireland's Kris Meeke, who had led on the second day before going on to finish third, more than half a minute behind the winner.
The 11th round of the championship takes place in France from 1-4 October with the 13th and final round, the Wales GB Rally, being staged from 12-15 November.
Commemorations have taken place across Wales to mark the 70th anniversary of Victory in Japan day.
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Sebastien Ogier secured his third successive World Rally Championship with victory in Rally Australia.