He attended the Tekniske Skole in Copenhagen from 1911 until 1914 before studying architecture at the Polyteknisk Laeranstalt from 1915 until 1917.
From 1920 Henningsen worked as an independent architect while also working as a journalist, writing for numerous journals and newspapers. Poul Henningsen became famous worldwide as the designer of lighting made by the Copenhagen company of Louis Poulsen.
Finding the style of traditional lighting designs to be insufficient for his interiors he began creating his own solutions. Henningsen was depressed by "how dismal people's homes are," and realised that "electric light gave the possibility of wallowing in light." Henningsen was evangelistic towards the development of modern lighting.
"PH" lamps were the results of the ten years Poul Henningsen spent developing lighting that was not glaring but shed warm, soft light. The first lamps in the "PH" range were shown at the 1925 "Exposition Internationale des Arts Décoratifs et Industriels Modernes" in Paris, where they were universally acclaimed. From the mid-1920s, Poul Henningsen's lamps were sold with great success all over the world.
By the time Poul Henningsen died in 1967, he had created more than one hundred lamps for the "PH" range, all of them based on the original idea of multiple shades and diffusors to provide warm, diffuse light. Among Poul Henningsen's best known designs is the "PH Louvre" (1957), a pendent ceiling lamp featuring thirteen concentrically arranged metal shades that scatter light on all sides. In 1958 Poul Henningsen created the "PH Snowball", a pendent lamp with eight aluminium shades.