Neighbouring Norway's royals did not however attend, staying at home as their nation reels from a deadly helicopter crash which killed 13 oil workers the day before.
On a day of pageantry and colour, the Swedish king was cheered by onlookers as he reviewed the royal guard. Later Gustaf and his family appeared on the palace balcony, cheered by thousands.
In the courtyard of the Royal Palace in Stockholm. Photo: TT
The list of invited royalty included Queen Margrethe II of Denmark, King Philippe of Belgium, Prince Albert II of Monaco, Princess Beatrix of the Netherlands, Princess Takamado of Japan and Jordan's Prince Raad bin Zeid and Princess Majda Raad Zeid.
But members of the Norwegian royal family cancelled after a helicopter carrying North Sea oil workers crashed on Friday near Bergen, Norway's second biggest city.
Prince Oscar made his first official appearance to celebrate his grandfather's birthday. Photo:TT
Born on April 30th, 1946, Carl Gustaf Folke Hubertus Bernadotte was only nine months old when his father, Prince Gustaf Adolf, was killed in a plane crash in Denmark.
He assumed the throne in 1973 following the death of his grandfather, the long-reigning Gustav VI Adolf.
The king has for many years struggled to shed his image as a car-mad playboy after being thrust onto the throne at age 27.
His finest hour came in January 2005, after some 500 Swedes lost their lives in the tsunami that swept across tourist resorts in southeast Asia.
“What if I, just like the king in the fairytales, could make everything all right and end the story with 'and then they all lived happily ever after',” he said.
“But I, just like you, am just a grieving, searching, fellow man,” he said in a speech at the time.