Moderate party leader Fredrik Reinfeldt declared victory and Prime Minister Goran Persson conceded defeat, announcing that he and the government would resign, the BBC reported.
The center-left party has governed Sweden for 79 of the past 89 years.
Reinfeldt campaigned on a pledge to cut taxes and reform Sweden's welfare state.
"We ran in the election as the New Moderates," he told supporters after declaring victory, "we have won the election as the New Moderates and we will also together with our Alliance friends govern Sweden as the New Moderates."
Persson said he would step down as Social Democrat party leader next March.
"We have lost the election but we are not a beaten party," he said. "We will never accept the right's change of system -- we will hit back."