During World War I he served in the US Army. After enlisting in the United States Navy in January 1919, he initially served on the destroyer Litchfield..
By 1941, he had become a Chief Watertender onboard the training and target ship Utah. When that ship was torpedoed during Japan's raid on Pearl Harbor, Tomich was on duty in a boiler room. The Utah was hit by two torpedoes from attacking Japanese planes. The order was given to abandon ship. But Tomich, up on the deck, pushed his way through the men, yelling that he had to get down to his men and his boilers before they blew up. As the Utah began to capsize, he remained below, securing the boilers and making certain that other men escaped. His actions cost him his life.
Tomich's devotion to duty and his brothers in arms did not go unnoticed. For his "distinguished conduct and extraordinary courage", he was posthumously awarded the Congressional Medal of Honor by President Franklin D. Roosevelt on March 4th, 1942.
The escort ship USS Tomich (DE-242), 1943-1974, was named in honor of Chief Watertender Peter Tomich.