Shortly after his education, he was drafted to fight in the Franco-Prussian war, and served from July 1870 to March 1871 in the Garde Nationale Mobile de la Seine.

[citation needed] Around 1874, Caillebotte had met and befriended several artists working outside the Académie des Beaux-Arts, including Edgar Degas and Giuseppe de Nittis, and attended (but did not participate in) the First Impressionist Exhibition of 1874.

[4] Caillebotte made his debut in the second Impressionist exhibition in 1876, showing eight paintings, including Les raboteurs de parquet (The Floor Scrapers) (1875), his earliest masterpiece.

[7] Its subject matter, the depiction of labourers preparing a wooden floor (thought to have been that of the artist's own studio) was considered "vulgar" by some critics and this is the probable reason for its rejection by the Salon of 1875.

Many of his paintings depict members of his family; Young Man at His Window (Jeune Homme à la fenêtre) (1876) shows René in the home on rue de Miromesnil;[12] The Orange Trees (Les Orangers) (1878), depicts Martial Jr. and his cousin Zoé in the garden of the family property at Yerres; and Portraits in the Country (Portraits à la campagne) (1875) includes Caillebotte's mother along with his aunt, cousin, and a family friend.

He often used a soft impressionistic technique reminiscent of Renoir to convey the tranquil nature of the countryside, in sharp contrast to the flatter, smoother strokes of his urban paintings.

In Oarsman in a Top Hat (1877), he effectively manages the perspective of a passenger in the back of a rowboat facing his rowing companion and the stream ahead, in a manner much more realistic and involving than Manet's Boating (1874).

The latter is almost unique among his works for its particularly flat colors and photo-realistic effect, which give the painting its distinctive and modern look, almost akin to American Realists such as Edward Hopper.

[17] Showing little allegiance to any one style, many of Caillebotte's other urban paintings produced in the same period, such as The Place Saint-Augustin (1877), are considerably more impressionistic.

[21] He ceased showing his work at age 34 and devoted himself to gardening and to building and racing yachts, and he spent much time with his brother, Martial, and his friend Auguste Renoir.

Although he never married, Caillebotte appears to have had a serious relationship with Charlotte Berthier, a woman eleven years his junior and of the lower class, to whom he left a sizeable annuity.

[9] In 1890, he played a major role in assisting Claude Monet in organizing a public subscription and in persuading the French state to purchase Édouard Manet's 1863 Olympia.

[9][29] In 2024, the Musée d'Orsay hosted an exhibition examining how Gustave Caillebotte depicted men in unconventional ways, hinting at his possible homosexuality.

The exhibition’s introductory texts highlight how Caillebotte portrayed men in domestic, often intimate settings typically reserved for women in the 19th century.

This collection of sixty-eight paintings, included works by Camille Pissarro (nineteen), Claude Monet (fourteen), Pierre-Auguste Renoir (ten), Alfred Sisley (nine), Edgar Degas (seven), Paul Cézanne (five), and Édouard Manet (four).

[35] The remaining twenty-nine paintings (one by Degas was taken by Renoir in payment for his services as executor) were offered to the French government twice again, in 1904 and 1908, and were both times refused.