On December 16, 2015, Thomas tied his then-career high of 38 points in a 119–116 loss to the Detroit Pistons. On January 28, 2016, he was named an Eastern Conference All-Star reserve for the 2016 NBA All-Star Game. Thomas became the lowest draft pick to be named an All-Star since the NBA draft was reduced to two rounds in 1989. He also became only the ninth player under to be named an All-Star, while also tying Calvin Murphy as the shortest player to be selected for the All-Star Game. On February 8, 2016, he was named Eastern Conference Player of the Week for games played Monday, February 1, through Sunday, February 7. Thomas led the Celtics to a 4–0 week, including a road victory against the Eastern Conference-leading Cleveland Cavaliers while averaging 20.3 points (12th in the East), 7.0 assists (tied for fourth in the conference), and 4.5 rebounds. With the Celtics down 2–0 to the Atlanta Hawks in the first round of the 2016 playoffs, Thomas scored a then-career-high 42 points in Game 3 in Boston to lift the Celtics to a 111–103 win. He became only the ninth Celtic to score 40 points in a playoff game. With 28 points in Game 4, Thomas helped the Celtics even the series at 2–2 with a 104–95 overtime win. However, the Celtics went on to lose the series 4–2.