McNicoll, with the financial support of her family through connections with renowned art collectors, was able to devote her time to painting.

McNicoll's first exposure to art presumably came from observing her parents—her father did sketches during his railway travels, while her mother painted china and wrote poetry.

McNicoll navigated the social side of the art world through lip reading and assistance from friends and family.

[2] From 1902 to 1904 McNicoll moved to London to study at the Slade School of Fine Art with Philip Wilson Steer; she may have met her lifelong partner Dorothea Sharp at this time.

In 1905, she attended Julius Olsson's School of Landscape and Marine Painting studying with Algernon Talmage.

As a director of the AAM school, Brymner also encouraged French art trends such as sketching in plein air, naturalism, and impressionism.

[2] While studying at the Slade School, McNicoll met British painter Dorothea Sharp with whom she formed a lifelong bond, nicknaming each other "Nellie" and "Dolly".

[7] In 2024, the exhibition Helen McNicoll: An Impressionist Journey which presented more than 65 paintings by the artist, including 25 from the collection of Pierre Lassonde, was held at the Musée national des beaux-arts du Québec (MNBAQ).

McNicoll was consistently recognized in Canada for her treatment of light and air, bold use of color, and overall "quiet" artworks—possibly influenced by her deafness.