Lookinland was born in 1960 in Mount Pleasant, Utah, a small town eighty miles (128 km) south of Salt Lake City. He has a younger brother, Todd, who starred in The Blue Bird with Elizabeth Taylor, and an older sister, Terese. Lookinland grew up in The Church of Jesus Christ of Latter-day Saints. He is a self-professed Conservationist and "camping nut". He attended the private Chadwick School, on the Palos Verdes Peninsula, in Southern California, and graduated in 1978.

Lookinland provided the voice of Oblio in the 1971 animated film The Point!. Shortly after the final season of The Brady Bunch wrapped filming, he appeared alongside Jennifer Jones and Paul Newman in the 1974 disaster film blockbuster The Towering Inferno and on the 1970s TV show The Secrets of Isis.

Since 1987, Lookinland has been married to Kelly Wermuth, who worked as a script supervisor on Touched by an Angel. They have two sons: Scott (born 1990) and Joe (born 1993). He was portrayed by his son Scott in the TV movie Growing Up Brady. Lookinland is a self-described Deadhead, a veteran of over 100 Grateful Dead shows.

Lookinland reprised his role as Bobby Brady in the 1988 Christmas special A Very Brady Christmas and again in the 1990 sequel series The Bradys, in which Bobby Brady was involved in a racing-car accident, which made him a wheelchair user throughout the series. Lookinland spent several years as a television camera operator and made an uncredited appearance in the 2000 TV movie Growing Up Brady as Shorr, the camera operator during the Brady Bunch episode "Room at the Top".