Mucia was first married to Gaius Marius the younger, consul in 82 BC, despite his young age. This was a time of civil war, when Lucius Cornelius Sulla had an army ready to march on Rome and their opponents needed a charismatic leader. Young Marius was not known as a talented general, but he had his father's (Gaius Marius) name to back him. Sulla won this civil war and Young Marius committed suicide, leaving Mucia a childless widow. According to the proscription laws, she was forbidden to marry again.
Soon after Sulla, now dictator, changed his mind in respect to this young widow in particular. He needed to secure Pompey's loyalty and to do that, he arranged his marriage to Mucia around 81 BC. This marriage resulted in three children: Gnaeus Pompeius (Pompey the younger), the girl Pompeia (married to Faustus Cornelius Sulla) and Sextus Pompeius.
Between 76 and 61 BC, Pompey spends most of the time away from Rome, campaigning in Hispania against Sertorius, in the Mediterranean Sea against the pirates and in the East, fighting king Mithridates VI of Pontus. On the final return, in 61 BC, Pompey sends Mucia a letter of divorce. According to Cicero's personal correspondence, the motive was adultery. Mucia then disappears from the sources.