Dr. Lawrence Jacoby, played by Russ Tamblyn, is a highly eccentric psychiatrist. Born January 30, 1934, Jacoby grew up in Hawaii and remains fascinated by it.

Jacoby was seeing Laura Palmer as a patient prior to her murder. Jacoby confesses to FBI agent Dale Cooper he's not a good person, and he really doesn't care about his patients who see him as their friend. Laura changed all that, and Laura changed him. Laura was in pain and the reasons for that were so mysterious that Jacoby couldn't penetrate the walls she had built around it.

Dr. Jacoby is married to a Hawaiian woman who is only seen once in the course of the series. He is known for keeping cocktail umbrellas marked with dates of influential events that affected him. He is also a keen surfer. A recognizable trait of the Doc's were his glasses - one lens of which was blue, the other red. (He said they made the world look three-dimensional.) He also could do some conjuring tricks. Dr. Jacoby's character was inspired by the late ethnobotanist and shamanistic explorer Terence McKenna.