In 241 her father was appointed the head of the Praetorian Guard by the Roman Emperor Gordian III. In May that year, Tranquillina had married Gordian. She became a Roman Empress and received the honorific title of Augusta. Her marriage to Gordian was an admission by the young emperor of both political indispensability of Timesitheus and Tranquillina’s suitability as an empress.
Gordian and Tranquillina had loved each other and had a happy marriage. They showed much respect and admiration for each other. Tranquillina’s grace, sweetness and high morals made her very popular with Roman citizens and the Roman army. In 243, her father suddenly died and was replaced with Philip the Arab, as head of the Praetorian Guard. When Gordian was killed in February 244, Philip became the new emperor. Tranquillina survived her husband. She had no children with him.