As the Crimean War broke out, he was transferred to Petropavlovsk in June 1854. Dmitry and his two brothers—Pavel and Alexander—took part in the war. Pavel Maksutov served in the Black Sea Fleet and was on board the battleship "Paris" during the Battle of Sinop, while Alexander and Dmitry took part in the defense of Petropavlovsk during the siege of Petropavlovsk. Dmitry Maksutov commanded the legendary cannon battery No. 2, while his brother Alexander commanded the battery No. 3. After the battle, both were awarded with the cross of Order of St. George of the 4th degree (posthumously for Alexander Maksutov).