Crane heard William Morris lecture on Art and Socialism in 1884 and became a committed socialist on the spot. From then on he divided his time between designing wallpapers for the drawing rooms of the wealthy and drawing cartoons for Justice, Commonweal and The Clarion, the socialist newspapers of the day. He saw no contradiction: good design was a political act, and capitalism produced ugly objects.

He began as a children's book illustrator, apprenticed to the wood engraver W.J. Linton. His Toy Books for the publisher Routledge, produced from 1865 onward, used flat areas of colour, strong outlines and decorative borders influenced by Japanese woodblock prints and the Pre-Raphaelites. They were among the first mass-produced children's books to treat illustration as a design problem rather than an afterthought.

During a lecture tour of the United States he spoke in favour of clemency for the anarchists sentenced to death after the Haymarket Affair. His wealthy American patrons cancelled engagements. Crane did not retract.

He became Vice President of the Healthy and Artistic Dress Union, a movement promoting loose-fitting clothing in opposition to tight Victorian corsetry. He wrote The Claims of Decorative Art, arguing that decorative art was not a lesser form. He was Art Director of the Art Workers' Guild and the first president of the Arts and Crafts Exhibition Society.

He wanted to be taken seriously as a painter of allegorical canvases, but the galleries would not exhibit them. The children's books and the socialist cartoons are what lasted. Morris would have appreciated the irony.