A temporada 4 de Doc Martin foi transmitida em ITV1 de dimanche 20 septembre 2009 para dimanche 8 novembre 2009. Consiste em 8 episódios, o primeiro chama-se "Better the Devil" e o último "The Wrong Goodbye"..
Make an appointment with the brilliant but socially awkward and neurotic Doc Martin. When Martin develops an aversion to blood, he abandons his career as a celebrated London surgeon and becomes the only doctor in a sleepy small town where his tactless manner soon has the whole town in an uproar.