He studied painting at the Ecole des Beaux-Arts in Paris, with masters such as Alexandre Cabanel, Carolus-Duran and Félix Bracquemond.

The prince invited him to collaborate in the creation of the frescoes of the Grand Amphitheater of the Oceanographic Institute of Paris, for which he financed the construction.

A prolific painter, he produced numerous family portraits, landscapes (banks of the Seine, Normandy coasts, Joliette Port, the calanques of Marseille) as well as still lifes.

He suspended his activities again in 1914 to resume them at the end of the war until 1934, when he retired to Malmousque in his villa "L'Ouragan", exhibiting only at the Jouvene Gallery in Marseille.

"[2] He also produced numerous posters for the shipping companies, the Chargeurs Réunis,[3] the Messageries Maritimes and the Société Générale des Transports Maritimes à Vapeur, focusing on the intense activity of the Quais aux huiles and Quais aux blés in Rive-Neuve in Marseille.

[6] The main fresco, entitled The Princess Alice Bridge during a cruise encircles the high bay that separates the large room from the small one.

This vast composition shows the typical activities of an oceanographic cruise such as Prince Albert I of Monaco, the patron of the institute, had organized at the beginning of the 20th century.

Alexandre Brun is also known for his famous collection of Orchids, commissioned by his friend, the passionate and wealthy Parisian collector Louis Libreck.

He immortalized the most beautiful subjects of the collection, faithfully representing on dark wash the most minute details of a hundred of these rare, exotic flowers.