Teenager Steve Andrews (Steve McQueen) and his girl Jane Martin (Aneta Corsaut) are out parking and see a falling star. They drive out to try to find where the meteor landed. An old man (Olin Howland) has heard the meteor crash near his house. He finds the meteor and pokes it with a stick. The rock breaks open to reveal small jelly-like blob inside. This blob, a living creature, crawls up the stick and attaches itself to his hand. The man runs hysterically onto the road, where he is seen by Steve, who takes him to see the local doctor, Doctor Hallen.They reach the clinic when Doctor Hallen is about to leave. Hallen anesthetizes the man and sends Steve back to the crash site to gather more information. Hallen decides he must amputate the man's arm which is being consumed by the blob, calling in his nurse. However the blob completely consumes the old man. Now an amorphous creatureit eats the nurse and the doctor, while increasing in size.Steve and Jane return to the office and Steve witnesses the doctor's death. They go to the local police, the kindly Lt. Dave and cynical Sgt. Burt. Dave, Burt, Steve and Jane return to the clinic but with no sign of the creature or the doctor the police dismiss Steve's story. Steve and Jane are sent home with their fathers. However they sneak out and retrieve Steve's friends and their girls from the cinema Spook Show (Daughter of Horror) and successfully enlist their help warning the town.The blob, in the meantime, has consumed a mechanic and (off camera), the janitor in Mr. Andrew's grocery store and a bar room of late night drinkers. Investigating, Steve and Jane are confronted by the blob in the grocery store and seek refuge in the walk-in refrigerator. The blob starts to ooze in under the door but then retreats. They escape and set off the town's fire and air-raid alarms. The whole town gathers and demands to know what is going on. As the townspeople and police angrily confront Steve, the blob enters the Colonial Theater during the Spook Show. It engulfs and eats the projectionist and oozes into the cinema seating area. The patrons run screaming out of the theater alerting the assembled townspeople to the danger. The blob leaves the theatre but Jane's little brother appears from the crowd to confront the blob with his cap gun, before running into the adjacent diner. Jane and Steve run in after him but become trapped along with the owner and a waitress when the blob engulfs the diner.The Blob – now an enormous mass – engulfs the diner and begins to ooze in through the windows. The occupants seek refuge in the cellar. The police try to kill the Blob by dropping a power line onto it. This fails, and only sets the diner on fire. The people are trapped inside with no hope of escape. The diner's owner uses a CO2 fire extinguisheron the fire, which also causes the approaching blob to recoil. Steve remembers the blob recoiled from the refrigerator too, and tells Lt. Dave that the Blob cannot stand cold. Jane's father Mr Martin, the school principal, takes Steve's friends to the high school to retrieve fire extinguishers which are used to freeze the blob. Dave requests an airforce jet to transport the blob to the north pole to keep it frozen. Steve muses that this solution will be fine as long as the north pole stays cold. A military plane is shown dropping the blob into an Arctic landscape.The film ends with the words "The End", which then morph into a question mark, suggesting that the Blob may return (which it does fourteen years later - this time, to a Los Angeles suburb—in the sequel Beware! The Blob.