Swimming in lane eight after qualifying last for the final, Balandin hit the wall in 2 minutes 07.46 seconds to beat Josh Prenot of the US by seven hundredths of a second at the Olympic Aquatics Stadium on Wednesday, reports Xinhua.
Russia's Anton Chupkov was third, 0.24sec further back.
Japan's Ippel Watanabe, who set an Olympic record of 2:07.22 in qualifying for the final, finished sixth.
Balandin, 21, won the 200m breaststroke gold medal at the 2014 Asian Games in Incheon.
His victory was Kazakhstan's second gold medal of the Games after weightlifter Nijat Rahimov's triumph in the men's 77kg clean and jerk.
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