He supported his brother-in-law Lepidus in 44 BC after Caesar's murder, accompanying Lepidus over the Alps. The following year, Lepidus sent him with a detachment of troops to join Marcus Antonius at Mutina,[6] but refused to accept responsibility for the help which Silanus gave.[7] After falling out of favor with the triumvirs, in 39 he fled to Sextus Pompeius.[8] He was able to return to Antonius's service under the terms of the Pact of Misenum.[9]
A Silanus later served under Antonius in Achaea and Macedonia[10] from 34 to 32, with the title of Quaestor pro consule or perhaps Proquaestor.[11] Although the inscription in Achaea names a Silanus whose parents were named Marcus and Sempronia.[12] Around this time he was also elected as an Augur.[13]
Before the Battle of Actium, Silanus went over to Octavianus.[14] The future emperor raised him to the Patriciate in 30 BC,[15] and they held the consulship together in 25.[16][17]
Marcus may have married a woman named Manlia from the Manlii Torquati, based on his descendants names.[18] Silanus' grandson, Marcus Junius Silanus Torquatus, was consul in AD 19, and married a great-granddaughter of Augustus.[19]