Sehwag backed Ashwin, who was bought at last month's auction for Rs 7.6 crore, to lead the team well in the upcoming season, which starts on April 7 in Mumbai.
The former India captain also heaped praise on the 31-year-old, saying he was peerless when it came to understanding the nuances of the shortest format of the game.
"I am sure Ashwin will also do wonders for Kings XI Punjab this year. Hopefully, we will qualify for the playoffs and reach the final also," Sehwag said.
He added: "The best quality in Ashwin is he is very smart. He understands the T20I format better than anybody else because he used to bowl in powerplays and in the slog overs. He knows what to do in the shortest format."
Ashwin promises exciting brand of cricket from KXIP
Meanwhile, Ashwin said he was excited about the new role and promised an "exciting brand of cricket" from KXIP in the upcoming season.
"I am really excited to be taking on this responsibility. Somebody has given me the opportunity to try and showcase my captaincy skills for the first time," Ashwin said.
"I have played under MSD [Dhoni], Virat [Kohli] and Viru pa (Sehwag) as well. Reasonably, he has seen something in me and handed me this responsibility. Hopefully, I can gel really well with Virupa and we can come out on top.
"I will definitely give my best. We will have a lot of fun and play an exciting brand of cricket this year."
KXIP had teased fans on January 31 by coming up with a list of captaincy probables. Yuvraj Singh, who had led the team in 2008, was part of the list, which also had the likes of their recent recruits Chris Gayle, KL Rahul and Aaron Finch.
The Punjab-based franchise had retained only India all-rounder Axar Patel for Rs 12.5 crore ahead of the two-day IPL auction. The Preity Zinta co-owned franchise was one of the busiest teams at the auction in Bengaluru.
KXIP managed to completely revamp their side in a bid to win their first league title after 10 years of failed attempts. They spent almost their entire quota of Rs 80 crore and bought 21 players.