Lefebvre was in Paris at the time of the Storming of the Bastille in 1789 and, like his close friend, Michel Ordener, he embraced the French Revolution.

After his unit was disbanded early in the Revolution, Lefebvre entered the newly-formed National Guard of Paris, obtaining the rank of lieutenant, and was injured defending King Louis XVI's during a popular uprising.

He then commanded the vanguard of the Army of the Danube under Jean-Baptiste Jourdan in March 1799, although for the first week of the campaign he was incapacitated with ringworm and Dominique Vandamme replaced him temporarily.

In May 1799, Lefebvre, by then a well-known general of division, entered politics and was elected to the Council of Five Hundred, even presenting himself as a candidate for a seat in the Directory in replacement of Jean Baptiste Treilhard.

[2] For the duration of the War of the Third Coalition, Lefebvre commanded a reserve corps in Mainz as well as three departments on the left bank of the Rhine.

That same year, Lefebvre was tasked with suppressing the Tyrolean Rebellion, but was replaced in this command by Drouet d'Erlon after a series of setbacks.

[2] After the first Bourbon Restoration he was made Peer of France by King Louis XVIII (4 June 1814), but rallied to Napoleon during the Hundred Days.

In the 1931 anthology If It Had Happened Otherwise, the alternate history scenario "If the Moors in Spain Had Won" by Philip Guedalla has Napoleon appointing Lefebvre as King Youssef I of Granada after deposing the House of Boabdil, only to trigger an analog of the Peninsular War.