In 296 BC, in the midst of the Third Samnite War, Sempronius was elected as Praetor, a position which though inferior to that of consul, was frequently held by ex consuls at this time. In this year, there was news received in Rome that the Etruscans, who had allied with the Samnites against Rome, had invited the Umbrians and Gauls to join their cause as well. This struck great panic into the senators of Rome, particularly because of the Roman dread of Gauls which originated during the Sack of Rome nearly a century earlier, and thus they ordered that not only should all free men of fighting age take the military oath, but that regiments should be formed from those above optimal fighting age and freedmen. Since both consuls were away from Rome campaigning against the Etruscans, the Senate gave command of this army to Sempronius in his position as praetor, so that he may guard the city. These fears were alleviated however when the Samnite force invading Campania at the time was crushed by one of the consuls, Lucius Volumnius Flamma Violens, causing the Senate to order a joyous thanksgiving in thanks to the consul. Slightly afterwards, the Senate resolved to establish two colonies around Campania to protect the region, ordering the Plebeian tribunes to pass a plebscite to make Sempronius appoint three men to establish the colonies, which was soon done, though there was a dearth of colonists willing to settle in such a war torn territory. This year was the final one in which Sempronius was mentioned by our sources