At a San Francisco pet store, socialite Melanie Daniels (Hedren) meets lawyer Mitch Brenner (Taylor) who is looking to buy lovebirds for his sister, Cathy’s (Cartwright), 12th birthday. Recognizing Melanie from an unflattering incident reported in the newspapers, Mitch pretends to mistake Melanie as a shop employee. A somewhat contentious encounter ensues after the disapproving Mitch reveals he knows Melanie’s identity. Mitch leaves without buying anything. To make amends, and finding him attractive, Melanie buys the lovebirds and delivers them to Mitch’s apartment, only to learn he is away for the weekend at his family’s farm in Bodega Bay. Melanie drives there with the love birds, and meets the local teacher, Annie Hayworth (Pleshette). Annie previously dated Mitch, but ended it due to Mitch’s cold, overbearing mother who dislikes any woman in Mitch’s life. In town, Melanie rents a boat and crosses the bay to discreetly leave the lovebirds at the Brenner farm. Mitch spots Melanie during her retreat and drives into town to meet her at the dock. As Melanie approaches the wharf, a gull attacks her. Mitch tends her head wound inside the cafe, where Mitch’s mother, Lydia (Tandy) arrives, seeing Mitch’s car outside. Melanie returns to Annie’s house and asks to spend the night. At the farm, Lydia’s hens are suddenly refusing to eat. Lydia expresses her disapproval of Melanie to Mitch, due to her (exaggerated) reputation. Mitch calls Melanie and invites her to Cathy’s birthday party being held the next day. Shortly after, there is a violent thud at Annie’s front door where there is a dead gull at the threshold.
At Cathy’s party, Melanie privately tells Mitch about her troubled past, and her mother running off with another man when Melanie was Cathy’s age. During a game, the children are attacked and some injured by gulls. The following evening, as Melanie dines with the Brenners, sparrows swarm the house through the chimney. After, Mitch insists she delay driving back to San Francisco and stay the night. The next morning, Lydia visits her neighbor and discovers his eyeless corpse, pecked lifeless by birds, and flees in horror. As Lydia recovers at home, she fears for Cathy’s safety, and Melanie offers to pick her up at school. As Melanie waits outside the schoolhouse, a large flock of crows slowly engulf the jungle gym behind her. Anticipating an attack, she warns Annie. As they evacuate the children, the crows attack, injuring several children. Mitch finds Melanie at the restaurant. Outside, when a gas station attendant is attacked by gulls, Mitch and several other men assist him. Spilled gasoline ignites causing an explosion. During the escalating fire, Melanie and others rush out. More gulls attack, and Melanie takes refuge in a telephone booth. Mitch rescues her and they get back inside the restaurant. A distraught woman blames Melanie for the attacks, claiming they began with her arrival.
Mitch and Melanie go to Annie’s house to fetch Cathy. They find Annie’s body outside, killed by the crows while protecting Cathy. That night, Melanie and the Brenners barricade themselves in the family home, which is attacked by waves of birds that nearly breach the boarded-up doors and windows. During a lull, Melanie investigates a fluttering sound in the attic. Birds violently attack Melanie, trapping her until Mitch pulls her out. Melanie is badly injured and traumatized; Mitch insists they all drive to San Francisco to get Melanie to a hospital. As Mitch readies Melanie’s car for their escape, a menacing sea of birds has quietly gathered around the Brenner house. The car radio reports bird attacks on nearby communities such as Santa Rosa and the military may intervene. Cathy retrieves the lovebirds from the house and joins Mitch and Lydia as they carefully escort Melanie past a mass of birds and into the car. The car slowly drives away as thousands of birds are ominously perching.