The forces supporting Vitellius were divided into two armies for the march on Rome, one of them commanded by Valens. Valens' troops took a route through Gaul, probably to recruit additional soldiers (see below), before eventually joining with the other Vitellian army, led by Caecina, at Cremona. By then Galba had been killed and Otho had been proclaimed emperor at Rome. Otho's forces met the combined Vitellian armies at the first Battle of Bedriacum. Valens and Caecina won a decisive victory, and Otho committed suicide when he heard the news of his army's defeat. Vitellius was able to make a triumphant entry into Rome.
However the armies in the east had proclaimed Vespasian as emperor, and two armies supporting Vespasian marched on Rome. The first to reach Italy was composed of five legions from Pannonia and Moesia, commanded by Antonius Primus. Valens was ill at the time, so that the force that Vitellius despatched from Rome to counter this threat was commanded by Caecina. Caecina tried to betray Vitellius and proclaim Vespasian as emperor, but his army refused to follow his lead and put him in chains. By this time Valens had recovered from his illness and was on his way to join the army, but before he could arrive the second Battle of Bedriacum had been fought and the Vitellian forces defeated by Antonius.
Valens tried to continue the struggle, and departed by ship from Pisa for Gaul to try to raise new troops. He put in at Hercules Monoecus (modern Monaco) but was advised not to try to march inland as a procurator named Valerius Paulus had raised a strong force from former members of Otho's Praetorian Guard. These had been dismissed from the service after Vitellius' victory, but were only too ready to re-enlist to support Vitellius' rival. Valens therefore sailed on, and was cast up by a storm on the Stoechades (modern Iles d'Hyeres, near Toulon). Here he was caught by surprise by some galleys sent after him by Valerius Paulinus and captured. Paulinus sent him back to Italy, where he was executed by beheading at Urvinum (modern Urbino). His head was taken to Narni to be shown to the Vitellian troops who were still resisting there and had been hoping that Valens would return with reinforcements. The sight of Valens' head was enough to persuade them to surrender.
One anecdote says that he appeared on the music-stage hall at Nero's coming of age celebrations, not at the command of Nero but voluntarily. At the time this was frowned upon, and many people thought that he was merely a man of fashion.