He campaigned with his co-consul (Lucius Julius Libo) against the Sallentini, captured Brundisium, and thence celebrated a double triumph.

[2] During the First Punic War, he was elected suffect consul in 256 BC, in place of Quintus Caedicius, who had died in office.

[3] With his colleague, Lucius Manlius Vulso Longus, he fought and defeated a large Carthaginian fleet off the coast of Sicily – the Battle of Cape Ecnomus – and the two then invaded North Africa, landing at Aspis on the eastern side of the Cape Bon peninsula.

[5] Manlius was recalled to Rome and celebrated a naval triumph, while Regulus captured Tunis and entered negotiations with Carthage.

[5] Wintering in Tunis, Regulus engaged in negotiations with the Carthaginians but offered very harsh terms that were rejected; Scullard, in the Cambridge Ancient History, rejects the claims given in Dio that Regulus' terms were so harsh as to "amount to a complete surrender" as "scarcely reliable".

Scullard believes that it is more likely that the Romans would have required Carthage to vacate Sicily; the Carthaginians, unwilling to leave the western half of the island, would have refused such a demand.

[13][14] The first evidence of the legend emerges with fragments of Gaius Sempronius Tuditanus's history in 129 BC; in this account, the Carthaginians have him starved to death.

According to Augustine of Hippo in City of God (5th century AD), using similar wording as Cicero in Pisonem, the Carthaginians "shut [Regulus] up in a narrow box, in which he was compelled to stand, and in which finely sharpened nails were fixed all round about him, so that he could not lean upon any part of it without intense pain".