Mike Brady (Robert Reed), a widowed architect with three sons—Greg (Barry Williams), Peter (Christopher Knight), and Bobby (Mike Lookinland)—marries Carol Martin (Florence Henderson), who herself has three daughters: Marcia (Maureen McCormick), Jan (Eve Plumb), and Cindy (Susan Olsen). Carol and her daughters take the Brady surname. Included in the blended family are Mike's live-in housekeeper, Alice Nelson (Ann B. Davis), and the boys' dog, Tiger. (In the pilot episode, the girls also have a pet: a cat named Fluffy. Fluffy never appears in any other episodes.) The setting is a large two-story house designed by Mike, located in a Los Angeles suburb.The show never addressed what happened to Carol's first husband

In the first season, awkward adjustments, accommodations, gender rivalries, and resentments inherent in blended families dominate the storylines. In an early episode, Carol tells Bobby that the only "steps" in their household lead to the second floor (in other words, that the family contains no "stepchildren", only "children"). Thereafter, episodes focus on typical teen and preteen concerns such as sibling rivalry, puppy love, self-image, character building, and responsibility. Noticeably absent is any political commentary, especially regarding the Vietnam War, which was being waged at its largest extent during the height of the series.