In 40 BC he was captured in Gallia Narbonensis by Menodorus, a general of Sextus Pompey, but pardoned for his father's sake.
[3] When the triumvirs Mark Antony and Octavian wanted to settle their conflict with Sextus Pompey in the Pact of Misenum in the summer of 39 BC many exiles were allowed to come back to Rome, so Marcus Titius and his father did likewise.
After the Romans tried in vain to capture Phraaspa, the capital of Media Atropatene, they withdrew to Armenia, but on their way they were harassed by the Parthian army.
After his return from the Parthian war, Antony learnt of the arrival of Pompey and received his envoys to negotiate about an alliance.
Accordingly, Pompey was able to capture Lampsacus, Nicaea and Nicomedia, but then Titius arrived from Syria with his army and a fleet of 120 ships.
[8] Because Titius declined negotiations and enjoyed overwhelming naval superiority, Sextus Pompey burnt his fleet and integrated its crew within his land forces, intending to march through Bithynia to Armenia.
At night Pompey tried to reach the coast with lightly armed troops to burn Titius' fleet, but his half-brother Marcus Aemilius Scaurus betrayed the plan.
[10] Whether Titius executed Pompey on his own initiative, or by order of Antony or Munatius Plancus, is uncertain and was already disputed in ancient times.
In the latter case it was possibly not the triumvir himself but Munatius Plancus who gave the order, as Antony did not want to take sole responsibility, since his lover, the Egyptian Queen Cleopatra VII, was well-disposed towards Pompey and because of his reputation.
There, Titius, together with his uncle Munatius Plancus, Gnaeus Domitius Ahenobarbus and other leading followers of Antony tried in vain to persuade the triumvir to send Cleopatra back to Egypt.
[16] According to the ancient biographer Plutarch the two men changed their party because they were treated insultingly by Cleopatra due to their refusal of her participation in the war.
[19] The two deserters informed Octavian about the content of Antony's testament and the place where it was kept in the custody of the Vestal Virgins – they had both earlier signed it as witnesses.
[23] In about 13/12 BC Titius became governor of Syria as successor of Octavian's close friend and admiral, Marcus Vipsanius Agrippa.