Through his numerous books, articles, and translations of European art texts Pach brought the emerging modernist viewpoint to the American public.

Pach's fluency in French, German, and Spanish made it possible for him to understand and interpret the avant-garde ideas developing in Europe and translate them for the English-speaking audience.

He was able to communicate personally with many noted artists in Europe and Mexico and mediate between gallery dealers and museum curators on their behalf.

He studied with Robert Henri at the New York School of Art and went abroad to paint with William Merritt Chase in the summers of 1903 and 1904.

He was also a friend of José Clemente Orozco and Diego Rivera and helped organize the Mexican chapter of the Society of Independent Artists.

He thought of himself both an artist and a writer, despite advice from friends like art historian Bernard Berenson who urged him to devote his time to writing.

His writings include monographs on a wide range of subjects, social commentary on the art world, and a book on museum structures.

[3] In 1923, Pach wrote Georges Seurat, a book art historian John Rewald later cited by as an important text on the artist.

Pach considered Vincent van Gogh a seminal figure in the development of modern art and was the first historian to lecture on him in America.