Not a great deal is known about the career of Serranus, who was born into the Plebeian branch of the gens Atilia. By 109 BC had been elected to the rank of Praetor, and this was followed by his election as consul in 106 BC. Although noted by Cicero as being a "stultissimus homo" ("a most stupid man"), he managed to defeat Quintus Lutatius Catulus in the consular elections of that year.
After his consulship, he was one of the senators who participated in the violent suppression of the rebellion of Lucius Appuleius Saturninus in 100 BC. A probable supporter of Lucius Cornelius Sulla, it is possible that he was the Atilius Serranus who was murdered at the end of 87 BC on the orders of Gaius Marius and Lucius Cornelius Cinna during the Marian capture of Rome which ended the first phase of the civil war between Gaius Marius and Lucius Cornelius Sulla.
Lucius Cassius Longinus and Gaius Marius
| Consul of the Roman Republic
with Quintus Servilius Caepio
Publius Rutilius Rufus and Gnaeus Mallius Maximus