Siakam recorded 34 points, 18 rebounds, 5 assists, and 1 block in 38 minutes played of the NBA's season-opening game to help the Raptors beat the New Orleans Pelicans 130–122. He also matched his career-highs in both offensive rebounds and made free throws, and set a new career-high in field goals attempted. On 8 November, Siakam scored a career-high 44 points in a 122–104 win over the Pelicans. On 13 November, Siakam scored 36 points in a 114–106 win over the Portland Trail Blazers. On 1 December, Siakam scored 35 points in a 130–110 win over the Utah Jazz. On 23 January 2020, Siakam was selected to his first career All-Star nod, being named a starter in the 2020 NBA All-Star Game. On 26 January, Siakam would again score 35 points in a 110–106 win over the San Antonio Spurs. On 21 February, Siakam scored 37 points, along with 12 rebounds, in a 118–101 win over the Phoenix Suns. On 16 September, Siakam was named to the All-NBA Second Team.