Armed Forces Day is a UK-wide event to support and celebrate serving and veteran military personnel.
Northern Ireland's event coincides with its host town's maritime celebrations - the Sea Bangor Festival.
Ards and North Down Mayor, Robert Adair, told the BBC more than 35,000 people had come to Bangor on Saturday.
Mr Adair said there was a "family friendly" atmosphere for the joint festivities and it was a great opportunity to thank those who serve.
"I'm so encouraged to see the turnout of people," the mayor said.
He said he was looking forward to "getting out there to meet as many of these brave men and women of our armed forces as possible".
Ards and North Down Council is co-ordinating the festivities, which include "breathtaking" Spitfire displays, tall ships, music, street theatre and food stalls.
For military historians and collectors, a wide display of memorabilia was put on display at a military fair at First Bangor Presbyterian Church Hall.
According to the council it included antique guns, swords, uniforms, medals, badges, stamps and coins.
As well as the parade on Saturday morning, military personnel performed a drumhead service and beating retreat.
About 300 events are taking place across the UK to mark Armed Forces Day, with the biggest celebrations hosted by Liverpool.
Thousands of people have attended Northern Ireland's Armed Forces Day in Bangor, which culminated in a military parade through the County Down town.