Aubameyang left Borussia Dortmund for the Gunners yesterday in a €63m deal.
And Bayern Munich striker Lewandowski thanked his former teammate for pushing him to a new level while they were together at BVB.
"Good luck Aubameyang, it was a pleasure to compete with you," said Lewandowski. "Only a healthy fight pushes us forward."
Aubameyang is in line to make his Gunners debut this weekend against Everton.