Pierre Georges Jeanniot was taught by his father Pierre-Alexandre Jeanniot, who for a long time was director of the art college in Dijon. He embarked on a military career, but exhibited watercolours as early as 1872 at the Paris Salon. In 1873, he exhibited his first oil painting there, Le Vernan at Nass-sous-Ste-Anne, and continued to show work there regularly. In 1881, having reached the rank of captain, he left the army in order to work full time as an artist. He settled in Paris, where he won an honourable mention in the Salon of 1882, a third-class medal in 1884 and a silver in 1889 and 1900. His was an assured and independent mind, and so he joined the Société Nationale des Beaux-Arts as soon as it was set up in 1890. He was made a Chevalier of the Légion d'Honneur.
The earliest works he sent in consisted mainly of scenes of military life. Later he was best known for his scenes of fashionable women in Paris at the time of the Belle Époque and on the beaches of the then very new seaside resorts, and for his views of race-meetings, all of these providing valuable sociological evidence. He also illustrated many literary works, among them Maupassant's Contes choisis (1886), Germinie Lacerteux (1886), Goncourt's La fille Élisa (1895), and Daudet's Tartarin de Tarascon (1887). He collaborated on the illustration of Victor Hugo's Les Misérables in 1887 and also illustrated Zola's La Débâcle and The Rat-Race (La Curée) of 1893-1894, Octave Mirbeau's Calvary (Le Calvaire) of 1901, Molière's Le Misanthrope in 1907, Balzac's The Peasants (Les Paysans) in 1911, Les Liaisons dangereuses by Laclos in 1917, as well as Voltaire's Candide and the Voyage à St-Cloud and other works. He was one of those who launched Modern Life (La Vie Moderne), and later he directed the Journal amusant. His drawing is vigorous and expressive, and his great strength lay in his brilliant depictions of the comedy of contemporary life.