The whole play takes place at Professor Serebryakov's country house, which is inhabited year-round by his daughter, Sonya, his late wife's mother, Mariya, and his late wife's brother, Ivan, or Vanya. They're like his secret, leftover family while he lives it up with his new, hot wife in the city.
Marina, the housekeeper/nanny who is like part of the family, sits with Doctor Astrov and Vanya in the garden. They all complain about how life has gotten complicated ever since Serebryakov showed up to stay at the house with his much-younger new wife, Yelena. No one gets any work done with those two around and the schedule is all out of whack.
Speak of the devil, Serebryakov, Yelena, Sonya, and a poor neighbor, Telegin, show up and join the others for tea. Mariya joins them, but she's upset by her son Vanya's yapping about his frustration with his life, most of which is directed toward Serebryakov. Dr. Astrov joins the old-man complaining contest, but his beef is about the environment. No, seriously: he's very concerned about the destruction of the Russian forest.
After all the griping is over, Vanya turns his attention to the Professor's new wife, Yelena. He's really into her and thinks that she's wasting her youth on the old man. She doesn't seem too interested in what he has to say.
Later on, at night, we find out that Serebryakov is a sick man who is almost always in pain. His wife and daughter run around trying to calm him, but nothing really helps. Vanya tries again to get some lovin' from Yelena, but she refuses him. Dr. Astrov shows up drunk, and Sonya, who is secretly in love with him, begs him not to drink. He agrees, but seems to be totally oblivious of that fact that she's got a mad crush on him.
Unsurprisingly, Sonya and her stepmother (who isn't too much older than she is) don't get along too well. After the doctor leaves, though, they make nice.
During the day, Serebryakov assembles the family and wants to make an announcement. While they wait for him, Vanya tries again to get Yelena to respond to his advances, but she gets mad at him.
Sonya and Yelena have a heart-to-heart. Sonya says she's crazy for Astrov but he doesn't notice her because she isn't pretty. Yelena promises to find out what he thinks, and Sonya gets nervous about the prospect of knowing the truth.
Yelena asks Astrov whether he loves Sonya. He says he doesn't love Sonya, and he takes the opportunity to class it up and try and kiss Yelena. Hey, it turns out that she's into him, too (traitor!), but Vanya sees their almost-kiss and Yelena freaks out. She wants to leave the country house and get back to the city ASAP. We can't imagine why.
Serebryakov announces, at the family meeting, that he's in financial trouble and is planning to sell the house and invest the money. He and the new wife will move to Finland. Vanya doesn't like the idea and reminds Serebryakov that he, Sonya, and his mother have been working for free, taking care of the house all this time, and that Serebryakov will leave them with nowhere to go.
Vanya gets really upset and blames his brother-in-law Serebryakov for all his life's problems. Vanya leaves, and Serebryakov follows him. Shots are fired, but old deadeye Vanya misses the professor. Twice.
In the last act, the doctor is trying to leave but he is missing a bottle of morphine, which Vanya has stolen. Sonya gets him to give it back. Yelena and Serebryakov leave, and everyone goes back to their ordinary lives again.