Ferlin had a minor career as an actor and debuted at the age of seventeen in Salomé by Oscar Wilde. He continued his career with a traveling theater company.
Although many of Ferlin's poems are melancholic, they are not without humor. Several were set to music and became popular songs such as En valsmelodi, an attack on the music industry. Ferlin sold over 300,000 volumes of his poetry during his lifetime. His lasting appeal is partly attributed to his vivid portrayal of central Stockholm before urban renewal and his association with the popular culture that flourished there then.