The monarch was joined by Queen Silvia, Crown Princess Victoria and Princess Madeleine at the ceremonial opening of the Riksdag session.
He used his speech to members of parliament to call for the United Nations' so-called Millennium Development Goals for poverty reduction to be made a top priority. The Development Goals include an aim to halve poverty by 2015, provide water and basic education to all and to stop the spread of HIV/Aids.
"Half this period has already passed and the international community faces a major challenge, as we have a long way to go," the king said.
Carl Gustaf also told politicians assembled in the Riksdag's chamber that the world was more interdependent than ever before. It was vital to work for increased knowledge and mutual respect across cultural and religious boundaries, he said.
The royals had earlier attended a dedication service at the Storkyrkan church in Gamla Stan along with many politicians. They were then taken in horse-drawn carriages the short distance to parliament.