The Carpathia was on its regular voyage to New York City, when early on 15 April 1912 it received a distress signal from the White Star Line ocean liner Titanic, which had struck an iceberg and was sinking. Rostron was asleep when his wireless operator, Harold Cottam, by chance left his headset on while undressing for bed and so heard the signal. Cottam ran to Rostron's cabin to alert him. Rostron immediately ordered the ship to race towards the Titanic's reported position, posting extra lookouts to help spot and manoeuvre around the ice he knew to be in the area and extracted every bit of speed the ship’s engines could muster. Even so, Carpathia, travelling through dangerous ice floes, took about 3½ hours to reach the Titanic's radioed position. During this time Rostron turned off heating to ensure the maximum amount of steam for the ship's engines and had the ship prepared for the survivors; including getting blankets, food and drinks ready, and ordering his medical crew to stand by to receive the possibly injured survivors.
Altogether, a list of 23 orders from Rostron to his crew was successfully implemented before Carpathia had even arrived at the scene of the disaster. Carpathia began picking up survivors about an hour after the first starburst was seen by those in the lifeboats. The Carpathia would end up rescuing 710 survivors out of the 2,228 passengers and crew on board the Titanic; at least one survivor is said to have died after reaching the ship. Later, Rostron testified about the events the night Titanic sank at both the U.S. Senate inquiry and the British Board of Trade's inquiry into the disaster.