Smith struggled over the first 10 games of the 2017–18 season. He got it going on November 7, scoring a season-high 20 points on 5-of-7 3-pointers in a 124–119 win over the Milwaukee Bucks, passing Rashard Lewis (1,787) for 14th place on the NBA's career 3-pointers made list. On December 14, in a 121–112 win over the Los Angeles Lakers, Smith passed Chauncey Billups (1,830) for 11th place on the NBA's career 3-pointers made list. On March 2, 2018, Smith was suspended by the Cavaliers for one game for throwing a bowl of soup at an assistant coach. During Game 1 of the NBA Finals against the Warriors, Smith got a free-throw rebound with 4.7 seconds left in regulation time. The game was tied, meaning that a field goal would have won the game. Smith, apparently confused and, thinking the Cavaliers were winning, attempted to dribble out the clock before realizing his error and frantically passing to George Hill with 1.2 seconds left, in front of a visibly-irate LeBron James. The Cavaliers lost 124–114 in overtime. In a post-game interview, Smith initially claimed to have known it was a tie game. He later backtracked, saying: "After thinking about it a lot... I can't say I was sure of anything at that point." The Cavaliers went on to lose the series in a four-game sweep.