The 26th overall pick by the 76ers in the 2018 draft, Shamet began his NBA career in Philadelphia before a mid-season trade to the Los Angeles Clippers. While a member of the Sixers, Shamet established himself as a regular part of the rotation. He hit three or more three-pointers 14 times, headlined by an 8-for-14 performance on Jan. 8 against the Wizards en route to 29 points. On Feb. 6, Shamet was sent to the Clippers, along with Wilson Chandler and Mike Muscala, in a six-player, four-draft-pick deal. In 54 appearances for the 76ers, Shamet averaged 8.3 points, 1.4 rebounds and 1.1 assists while shooting 40.4 percent from beyond the arc. In Los Angeles, he picked up where he left off, draining 45 three-pointers in the first 15 appearances for the Clippers. On March 1 against the Kings, Shamet went 5-for-10 from beyond the arc. One game later, in a win over the Knicks, he hit 7-of-11 attempts from deep. The rookie came off the bench for his first two games in a Clippers uniform, but he would go on to start the final 23 games of the regular season. Over that period, Shamet posted 10.9 points, 2.3 rebounds and 2.3 assists per game. He finished the season with the league's 11th-highest three-point percentage (42.2%), while also ranking in the top 10 in turnover percentage (7.0%). Shamet was named to the All-Rookie Second Team.