Aubameyang sealed a £56m ($78m) transfer from Borussia Dortmund to the Emirates Stadium on 31 January, while Mkhitaryan joined the Gunners earlier in the month in a straight swap deal that saw Alexis Sanchez move to Old Trafford.
Aubameyang and Mkhitaryan were teammates for three years at Dortmund, and the Gabon striker revealed that he was in touch with his former teammate in the days leading up to his transfer to Arsenal.
"It's like [being reunited with] a brother, a good friend," the 28-year-old was quoted as saying by Sky Sports.
"We played together in the past and I'm really happy to see him again. He called me a few times, he asked, 'Will you come or not?' I said, 'First you have to tell me if you sign or not'.
"He told me all was done and of course it was a big factor in coming here.
"We understand each other on and off the pitch, that's why it's easier on the pitch. [The fans] have to be happy [to see us together], we will do our best of course, like we did in the past."
Aubameyang scored off Mkhitaryan's pass on his Arsenal debut in the 5-1 win over Everton last weekend, with the Armenian also assisting two other goals.
Former Gunners striker Thierry Henry last week urged manager Arsene Wenger to revert back to a 4-4-2 formation to get the best out of Aubameyang and Alexandre Lacazette.
"[Lacazette] was like the next best thing and came with a big transfer fee like Aubameyang too, so hopefully they can play at times together up front," Henry told Sky Sports.
"In my day we played a rigid, flat 4-4-2 and that was it. I don't think Arsene will go back to that but why not?"