In another contest, Canada overwhelmed China 9-2 in a matchup of medalists from the 2010 Games in Vancouver.
Sweden let an early 3-0 lead get away before moving in front for good by scoring twice in the seventh end.
The Canadians, who fell to Sweden in the gold-medal game at the last Olympics, ensured themselves the win over China with a three-point fifth end that gave them a 6-1 lead.
In the other opening matches of the women's curling tournament, Switzerland defeated the United States 7-4 and Russia won over Denmark 7-4. Neither Japan nor South Korea was in action Monday.
The 10 teams engage in a round-robin tournament throughout the Olympics with the top four in the final standings moving into the semifinals.