Leloir was the son, and pupil, of painter Auguste Leloir and watercolorist Héloïse Suzanne Colin, daughter of painter Alexandre-Marie Colin.
His brother, Alexandre-Louis Leloir was also a well known painter and illustrator.
Leloir married Céline Bourdier, with whom he had a daughter, Suzanne Leloir, who married Philippe, the son of Pauline Savari in 1912.

Leloir first exhibited his work at the Salon des artistes français, of which he became the secretary.
With many other painters, he was a member of the Crozant School in the valleys of Creuse.
In 1907, he was the founding president of the Société de l'histoire du costume, and he donated the family's collection of fashion prints to the society.

Around the 1890s, Leloir and his students flooded the picture book market, inspired by photographs representing accurately costumes and attitudes of the past, much appreciated by bibliophiles.
He was a prolific illustrator of books, especially for children, such as the Richelieu by Théodore Cahu, of magazines and fans.

In 1884, Guy de Maupassant dedicated the short story Idylle to Leloir.


In 1929, Leloir traveled to Hollywood at the urging of Douglas Fairbanks to work on his last silent film, The Iron Mask.
He chronicled his experiences in his memoir Five Months in Hollywood with Douglas Fairbanks.
Leloir was the son, and pupil, of painter Auguste Leloir and watercolorist Héloïse Suzanne Colin, daughter of painter Alexandre-Marie Colin. His brother, Alexandre-Louis Leloir was also a well known painter and illustrator. Leloir married Céline Bourdier, with whom he had a daughter, Suzanne Leloir, who married Philippe, the son of Pauline Savari in 1912.
Leloir first exhibited his work at the Salon des artistes français, of which he became the secretary. With many other painters, he was a member of the Crozant School in the valleys of Creuse. In 1907, he was the founding president of the Société de l'histoire du costume, and he donated the family's collection of fashion prints to the society.
Around the 1890s, Leloir and his students flooded the picture book market, inspired by photographs representing accurately costumes and attitudes of the past, much appreciated by bibliophiles. He was a prolific illustrator of books, especially for children, such as the Richelieu by Théodore Cahu, of magazines and fans. 
In 1884, Guy de Maupassant dedicated the short story Idylle to Leloir.

In 1929, Leloir traveled to Hollywood at the urging of Douglas Fairbanks to work on his last silent film, The Iron Mask. He chronicled his experiences in his memoir Five Months in Hollywood with Douglas Fairbanks.
Maurice Leloir