After going undrafted in the 2017 NBA draft, Koenig signed a two-way contract with the Milwaukee Bucks on July 6, 2017. On September 21, 2017, the Bucks requested waivers on Koenig. A week later, he signed a training camp deal with the Chicago Bulls. He was waived on October 14 as one of the team's final preseason roster cuts. He would later participate with the Grand Rapids Drive for the 2017-18 NBA G League season. Koenig averaged 9.8 points per game and shot 40% from the three point arc in 47 games with Grand Rapids.
