Two very different teen boys, Drake and Josh, learn that they are suddenly becoming stepbrothers as their parents are marrying. Josh and his father move in with Drake, his mother and little sister. The two boys, especially Drake, have some trouble acclimating to living under the same roof.
When Josh gets grounded because of something that Drake did, Josh has the time to fix a broken dune buggy that their friend Trevor gave to the two boys. Drake takes the dune buggy out, against his parents wishes as he doesn't have a drivers license, and ends up getting hurt after he crashes into a tree. Josh blackmails Drake to tell his parents the truth.
Drake's new girlfriend keeps hitting on Josh when Drake isn't around. Things come to a head when she kisses Josh but then denies it, saying that it was Josh who kissed her. Josh will do anything to make Drake realize the truth.
Josh agrees to baby sit his dad's boss' baby when all the adults go out for dinner but has no idea how challenging the responsibility is. His situation gets even worse when Drake has to leave for a gig but soon returns home to help Josh when he hears how out of control the situation is.
Josh develops his first real crush on a girl at school but because he is so nervous and wants to impress her, mistakenly tells her that he can play the guitar and that he will play at her birthday party. He turns to Drake for help but Drake is banned from the restaurant where the party is taking place. The two work out a plan so Josh can still impress the girl and Drake can get back into the restaurant.
When their parents go out of town for the weekend, Josh and Drake are excited about having their freedom but that comes to an end when Josh's 'Grammy' comes to baby sit. Grammy won't let them leave the house so Drake sneaks out so he can go to a concert. When he ends up in jail, Grammy has to bail him out and is not happy about it.