Upon moving to Spain, he had over 40 children's books published, which earned him the SM Ediciones' International Illustration Prize in 2001.

His first drawings date from the period between 1952 and 1956,[1] but his professional career, as a cartoonist and artist, did not start until 1961, in New York City,[2][3] where he lived until 1969;[1] during this time he had his cartoons published in magazines such as Esquire, The New Yorker, The Atlantic (then The Atlantic Monthly) and The Reporter[2] He would return to his country in 1971, where he worked for the magazine Ercilla,[1] but in 1973 had to move to Sitges, Spain, in order to escape from the September 11 coup d'état.

[3] After receiving a fellowship from the John Simon Guggenheim Memorial Foundation,[4][5] he was able to produce his first animated film, El crimen perfecto, in 1976.

[3] Krahn contributed to newspapers such as El País, International Herald Tribune, Die Zeit and La Repubblica.

[4] Fernando had a daughter, called Fernanda,[3] and two sons Santiago and Matias and he was married to Chilean writer María de la Luz Uribe, who died in 1994.