The actor explained that he understands Pete's constant drive to find success in his professional and private lives.
"Pete feels emasculated, he feels a bit insecure about his place among the men of the world," Kartheiser told CNN.
"He doesn't have that machismo or the elegance of the men that surround him. I think I can relate to some of those things and some of the way Pete hates himself and worries that the world hates him for those things too."
The star went on to say: "Now, granted, I'm not trying to say I'm Pete Campbell. Those issues reside in me as deeply as they do him. But I have understood those through my life. I think most people can.
"I think if people took a fearless look at themselves, they'd see a lot more Pete Campbell than they'd want to believe."
Kartheiser also shed light on his relationship with Mad Men creator Matthew Weiner and the show's various directors.
"Every director brings a little taste of themselves. At the end of the day, Matthew Weiner has final cut," the actor commented. "At the end of the day, Matthew Weiner will re-shoot a scene if it doesn't fit into the look of the show. That's wonderful.
"Everyone has stylistic differences and he wants them to express those things, but he wants to make sure that there's a consistency to the look of the show, to the tone of the show. That being said, I absolutely love John Slattery as a director. He loves the art form of it."
Kartheiser recently suggested that Pete Campbell's unhappiness is rooted in his unsatisfying marriage to wife Trudy (Alison Brie).
Mad Men airs on Sundays on AMC in the US, and Tuesdays on Sky Atlantic in the UK.
Watch a Mad Men trailer below: