On July 6, 2012, Motiejūnas signed a four-year, rookie scale contract with the Houston Rockets and joined them for the 2012 NBA Summer League.
In his summer league debut, he recorded 25 points, 9 rebounds, 2 assists, 2 steals and 1 block.
After the game, he quoted a famous Lithuanian idiom describing his debut: "Jeigu bijai vilko – neik į mišką" (English: If you're scared of wolves, don't go into the woods).
Overall, he averaged 16.3 points and 7.8 rebounds in four games.

On November 14, 2012, Motiejūnas was assigned to Rio Grande Valley Vipers of the NBA Development League.
In his D-League debut on November 23, he recorded 31 points, 8 rebounds, 3 assists and 1 steals.
Two days later, he was recalled by the Rockets.
He was later reassigned two more times throughout the season and in seven D-League games, he averaged 20.3 points, 9.7 rebounds and 3.0 assists per game.
In 44 games for the Rockets, he averaged 5.7 points and 2.1 rebounds per game.
On July 6, 2012, Motiejūnas signed a four-year, rookie scale contract with the Houston Rockets and joined them for the 2012 NBA Summer League. In his summer league debut, he recorded 25 points, 9 rebounds, 2 assists, 2 steals and 1 block. After the game, he quoted a famous Lithuanian idiom describing his debut: "Jeigu bijai vilko – neik į mišką" (English: If you're scared of wolves, don't go into the woods). Overall, he averaged 16.3 points and 7.8 rebounds in four games.
On November 14, 2012, Motiejūnas was assigned to Rio Grande Valley Vipers of the NBA Development League. In his D-League debut on November 23, he recorded 31 points, 8 rebounds, 3 assists and 1 steals. Two days later, he was recalled by the Rockets. He was later reassigned two more times throughout the season and in seven D-League games, he averaged 20.3 points, 9.7 rebounds and 3.0 assists per game. In 44 games for the Rockets, he averaged 5.7 points and 2.1 rebounds per game.
Donatas Motiejūnas