Widower Steve Douglas raises three sons with the help of his father-in-law, and is later aided by the boys' great-uncle. An adopted son, a stepdaughter, wives, and another generation of sons join the loving family in later seasons. Disney producer Bill Walsh often mused on whether the concept of the show was inspired by the movie The Shaggy Dog, as in his view they shared “the same dog, the same kids, and Fred [MacMurray].
Chip Douglas is so nervous about taking his driving test that his new sister in law Katie decides to help by taking the test with him. Soon after they both get their driving licenses the family car collects a big scratch, but neither will plead guilty.
A Special time consuming project keeps Steve and son Robbie so pre-occupied that they are tired when they arrive home. After the project ends, the co-workers throw a celebration party and when Barbara and Katie arrive with supper for their hardworking spouses, and see a party in full swing, they storm out.
Katie tearfully complains when Uncle Charley makes her feel unnecessary in the Douglas household. Steve speaks to Charley who is flabbergasted at the accusation, but immediately makes amends. Meanwhile, Chip is on a five-man school committee; four of the 'men' are girls and they won't let him open his mouth.
While Steve and Bub are away, Chip, Robbie and Mike face the problem of caring for two sick foundlings, a wild bird and a frightened girl, who they learn is a runaway from a maid's job in Philadelphia where she has been unhappy.
When her brothers have more pressing commitments, Steve gets cast in Dodie's school play as a tree, more or less proving Robbie's point that females are instinctive manipulators.
Chip's schoolmates want to help him celebrate his tenth birthday with a party but he doesn't want to share the occasion with certain young ladies. However, Steve falls foul of the German measles and when Bub speaks to Sudsy's mother about it, suddenly the gossip mongers decide that they will not send their children to the house for fear of catching the disease.
A genial bum Ernie brings home for dinner outrages Uncle Charley by eating everything in sight and then decides to stay the night even though he wasn't invited. Steve feels that they should let Ernie work things out for himself.
Barbara is jealous when a glamorous special secretary enters the lives of both Steve and his son, Robbie, and causes a double domestic crisis. Barbara ends up consoling a heartbroken young lady who is eventually fired from her position.
While Steve becomes pre-occupied with a time-consuming project named Taurus, Barbara blossoms forth as a Championship Cook. Her recipe for 'Tangy Tidbits' wins her a trip to Hawaii for the final cookout.
Little Dodie feels out of place among her three stepbrothers and her often grumpy uncle, and discovers that being a member of the Douglas family can be a rough and tumble proposition.
Hoping to renew her funloving friendship, Steve's old girlfriend from Bryant Park, who is now a rich divorcee, comes to town and gives Barbara a few jealous moments.
Ernie is left in charge for one day when Steve and Barbara are off to Chicago for a golf tournament while Uncle Charley attends a string music festival. Little Dodie and her friend take a shopping excursion into town but don't have enough money for the bus ride home.
Chip complains about Polly's lack of sales resistance because they have an apartment full of useless things. But she is trapped by a salesman into giving a dinner party for eight people in exchange for a free set of cookware.
When Chip adopts a Beatle-style, shoulder length haircut, the other members of the family feel that Steve should lay down the law to the long-haired one, but he and his associate consult a company psychologist for a solution. Steve decides not to be a strict father but to give the boy more attention, without affect.
A boy who looks just like Robbie almost ruins his reputation by driving around on-campus and inviting strange girls to kiss him, before the deception is uncovered. Finally, both boys and their parents are brought to the dean's office.
For their fourth week wedding anniversary, Katie decides to earn some money for an expensive gift for Robbie by taking a one week job as a tea-room waitress. Robbie lunches at the tea-room and finds Katie, who has taken over as a last-minute replacement for the cigarette girl, in an abbreviated costume.
Dodie studying piano, Margaret on the violin and Susan at clarinet, comprise the 'Rondelay trio' and Dodie tells Steve and Barbara the good news that they'll practice at the Douglas house for their upcoming recital.
Barbara leaves Ernie in charge of looking after Dodie after she has to go shopping. However Dodie goes to her friend Drucilla's house, and when Barbara returns he cannot remember where she is. After Dodie is found, Barbara sends them both to their rooms for the day. Then Ernie and Dodie rebel when they feel that they've been unjustly punished.
Childless young marrieds Chip and Polly Douglas suddenly find themselvs the temporary guardians of several young children including the triplets, when Katie flies to Peru for a weekend rendezvous with Robbie. Meanwhile, Steve, Barbara and Charley go on a camping trip and Barbara isn't exactly Mrs. Daniel Boone -- as Steve eventually finds out.
Katie's triplets are spotted by a talent scout for a production company and are selected to appear in a television commercial. The temperemental Director yells when the boys misbehave and make a shambles of the studio. Grandfather Steve is asked to replace the actor doing the same so the boys will feel at ease.
Dodie commits the entire Douglas family to a time consuming project - the awesome task of getting a four foot tall bag of Peanuts into small little sacks which they hope to sell at the school fair to raise money for Korean orphans.
The Douglas family becomes concerned about Dodie's despondency when Tramp, the ageing family mongrel, keeps disappearing at night. Meanwhile, Uncle Charley makes her a rag-doll and names it Arfie.
Chip decides to quit his Chemical Engineering studies in favour of a rock music career when he meets up with a former friend who is now a big star. When Barbara visits John in the studio she is baffled by all the switches on the recording console, and realises that professional musicians know what they're doing, so how will Chip handle it?
Ernie feels left out when the Douglas family orchestra begins to practise. Uncle Charley tries to teach Ernie the violin but runs into a major obstacle -- the boy's lack of obvious talent.