[1] Khismatullin won the silver medal at the Under 16 event of the World Youth Chess Championships in 2000.

[2] In 2011 he tied for 4th–10th with Rustam Kasimdzhanov, Gata Kamsky, Rauf Mamedov, Ivan Cheparinov, Maxim Rodshtein and Yu Yangyi in the Aeroflot Open in Moscow.

[3] He took part in the Chess World Cup 2011, where he was eliminated in the first round by Mikhail Kobalia.

[4] In 2013 Khismatullin tied for 1st–11th with Pavel Eljanov, Dmitry Kokarev, Alexander Areshchenko, Maxim Matlakov, Oleg Korneev, Dragan Solak, Vadim Zvjaginsev, Sanan Sjugirov, Ivan Bukavshin and Ildar Khairullin in the Chigorin Memorial in Saint Petersburg.

[6] In January 2014, Khismatullin won a friendly eight-game match with Salem A. R. Saleh by 7–1.

He finished third in the Superfinal of the 2014 Russian Chess Championship behind Igor Lysyj and Dmitry Jakovenko respectively.

[9] Khismatullin tied for 2nd–4th place with David Navara and Mateusz Bartel, finishing fourth on tiebreak, in the 2015 European Individual Chess Championship, held in Jerusalem.

This result qualified him for the Chess World Cup 2015,[10] where he was eliminated in the first round by Alexander Areshchenko.

That same year Khismatullin won the Rashid Nezhmetdinov Memorial tournament in Kazan.

[11] In December 2015 he won the Russian Rapid Grand Prix in Khanty-Mansiysk.

Khismatullin's own pro-war stance led to criticism of his stance by, among others, Polish player Jan-Krzysztof Duda, who refused to shake Khismatullin's hand during a 2023 match.

[13][14] El Pais called him "the most controversial participant" of the World Rapid Chess Championship in 2023.

[13] Denis Khismatullin vs Pavel Eljanov, 2015 European Individual Chess Championship, round 10:[15] 1. d4 Nf6 2. c4 e6 3.