Cousins, selected as a starter in the Western Conference and drafted by LeBron James, will miss the remainder of the season after rupturing his left Achilles tendon on Friday.
When a player is injured or unable to participate in the All-Star Game, commissioner Adam Silver selects the replacement, and in this case, George was added by virtue of having the most voting points from head coaches among Western Conference players not selected as a reserve.
"Obviously, I would have liked to make it under better circumstance -- because of an injury I got in," George said after the Thunder's 121-108 win over the Pistons on Saturday. "But needless to say, I'm happy for this to be my fifth and go alongside Russ [Westbrook] and, you know, be a part of this franchise to hold it down for the Thunder. I'm grateful for this opportunity."
Cousins was named as a starter, but the Team LeBron coach will make the decision as to who replaces him in the starting lineup.
George was not originally selected by the coaches as a reserve when teams were announced Tuesday, which drew criticism from teammate Russell Westbrook, who called it "outrageous."
"I don't know who else made the team, but got four people from one team, you've got guys complaining about getting snubbed until they get in, you've got guys just talking about it all the time," Westbrook said. "But the guys that deserve it -- should be in -- are not. I just don't understand. Doesn't make any sense."
George then told ESPN's Rachel Nichols that Westbrook's support and leadership were making this summer's free-agency decision "easier." Westbrook's comments also drew criticism from All-Star reserve selection Damian Lillard, who said he was "disappointed" in Westbrook's statement.
George, a native of southern California, will be making his fifth All-Star appearance and third straight. He's averaging 21.0 points, 5.5 rebounds, 3.0 assists and 2.17 steals per game in his first season with Oklahoma City, and he is shooting a career-high 42.6 percent from 3.
George said he "absolutely" looks forward to playing in Los Angeles.
"Being in front of family and friends, it has some significance to it," he said.
ESPN's Michael Rothstein contributed to this report.