As the 2012–13 season progressed, Petrov went on to land several clean 3A with positive GOE, including one at the 4th stage of the Cup of Russia series in November 2012.

Weeks later, at the 5th stage of the Cup of Russia series, Petrov landed a combined total of three clean 3A including a 3A-3T in the free skate.

On the international scene, Petrov won gold medals in the junior events at the 2012 Coupe de Nice and the 2013 20th Volvo Open Cup.

[5] In the 2013–14 season, Alexei Mishin began coaching Petrov alongside Tatiana Mishina and Oleg Tataurov.

[1] In November, Petrov competed in the first senior international of his career at the 2013 22nd Volvo Open Cup in Riga, Latvia and won the silver medal there.

He beat several experienced skaters including compatriots Sergey Borodulin and Zhan Bush, finishing behind 4-time Olympic medalist Evgeni Plushenko.

At the Russian Championships, Petrov ranked eighth on the senior level and improved on his previous showing by winning silver in the junior event, finishing 1.88 points behind Adian Pitkeev.

He went on to win gold in Tallinn, Estonia, outscoring Japan's Sota Yamamoto by 5.67 points, and qualified for his second consecutive Junior Grand Prix Final, where he would eventually take home the bronze medal after finishing second in the free skate.

Competing on the senior level at the 2014 Finlandia Trophy, he placed second in the short and third in the free skate, taking the bronze medal behind American Adam Rippon.

Petrov won his first international senior title at the 2014 Cup of Nice after placing first in both programs and outscoring fellow medalists Artur Dmitriev, Jr. and Keiji Tanaka by over thirty points.

[6] Illness took its toll on his performance at the World Junior Championships where he finished 6th overall after winning a bronze medal for the short program.

Eventually, the ISU decided to award points from the competition based on the placing of the skaters after the short program.

It was revealed after the event that he had in fact been carrying a ligament injury to his leg going into the competition, after falling badly just one and a half weeks before the Championships.

In 2016, Petrov started his season at the 2016 Nebelhorn Trophy where he won gold after placing first in both the short and free skate with a total of 232.21 points.