The son of Gnaeus Servilius Caepio, he served as consul in 140 BC alongside Gaius Laelius Sapiens.
After his consulship, Caepio was assigned to a proconsulship in Hispania Ulterior after the defeat of Quintus Fabius Maximus Servilianus at the hands of the Lusitanian chieftain Viriathus and the ratification of a treaty favourable to the latter.
[1][2] At the start of Caepio's tenure, he "pestered the senate with constant missives, urgently requesting permission to resume the war with Viriathus and disparaging Servilianus' dishonourable treaty".
[2] After getting permission to resume the war and with substantially more resources than Viriathus (who was running out of men), the chieftain opened negotiations, which were for naught: Caepio successfully bribed Viriathus' followers to assassinate him.
[6] His victory, however, was not complete: "other communities in western Spain were inspired by Viriathus' example and continued to raid the [Roman] provinces" in the coming years.