- Ryan's introduction and integration by Sandy Cohen into Orange County society, and his growing relationship with Marissa Cooper.
- The destruction of Marissa's relationship with her boyfriend Luke Ward, and his subsequent change in personality.
- Seth's love for Marissa's best friend, Summer Roberts, becoming a strange relationship.
- The marriage breakdown of Marissa's parents, Jimmy Cooper and Julie Cooper, as his business fraud was made public.
- Sandy's jealousy over Kirsten and Jimmy's old relationship.
- Sandy's changing of jobs from public defender to private attorney, which soon saw him disillusioned with the industry.
- Sandy and Jimmy eventually going into business with a restaurant, only to be bought out by Caleb Nichol.
- Ryan dealing with the manipulative Oliver Trask, who tried to take Marissa away.
- Caleb's manipulations and dirty business deals.
- Marissa dealing with a substance abuse problem of drinking and drugs.
- Seth having to choose between Summer and his good friend Anna.
- Julie's short-lived relationship with Luke, and her subsequent engagement to Caleb (which many suspected was simply for money).
- Ryan's ex-girlfriend and good friend Theresa, from Chino, who came to stay for a while and whose abusive fiancé Eddie forced her to flee.
- Sandy's overbearing mother, Sophie, (nicknamed 'the Nana') coming to stay and announcing that she was dying of cancer.
- Luke's discovery of his father's homosexuality and eventually moving away from Orange County (and the series).
- Kirsten's outgoing and spoiled younger sister Hailey Nichol, notorious for not doing anything with her life, coming to stay and developing a relationship with Jimmy.
In the season finale, many events came to a head: Caleb Nichol and Julie Cooper were married in a surprisingly uneventful ceremony; however Caleb revealed to Sandy Cohen that he was on the verge of bankruptcy. Marissa Cooper moved in with Julie and Caleb, but had redeveloped her drinking problem. Seth Cohen and Summer Roberts had problems after her father did not take a liking to him. Ryan Atwood discovered Theresa was pregnant, possibly by him, and decided to move back to Chino to support her. Most of all, Seth ran away on the Summer Breeze, his sailboat, distraught by Ryan's departure.
- Peter Gallagher as Sandy Cohen
- Kelly Rowan as Kirsten Cohen
- Benjamin McKenzie as Ryan Atwood
- Adam Brody as Seth Cohen
- Melinda Clarke as Julie Cooper
- Mischa Barton as Marissa Cooper
- Rachel Bilson as Summer Roberts
- Chris Carmack as Luke Ward
- Tate Donovan as Jimmy Cooper
In the first several episodes, neither Melinda Clarke nor Rachel Bilson were credited in the main cast. They were later added after fan support for their characters increased. Chris Carmack left the cast later in the season. While Alan Dale made several appearances as Caleb Nichol, he did not join the cast until Season 2.
|Picture||Title||Episode #||Writer||Episode #|
|Premiere||1.01||Josh Schwartz||August 5, 2003|
|After Ryan just escapes jail time and is kicked out by his mother, his attorney, Sandy Cohen, brings him home, to the dismay of his wife, Kirsten. Ryan meets their son, Seth, and other Newport teenagers whom lead him to trouble, making Kirsten think again about letting Ryan stay in their home.|
|The Model Home||1.02|| Allan Heinberg|
|August 12, 2003|
|Marissa and Seth convince Ryan not to leave Newport, and hide him in one of Kirsten's vacant model homes. When Luke confronts Ryan about his relationship with Marissa, their fights ends up setting the model home to fire, getting them both arrested.|
|The Gamble||1.03|| Allan Heinberg|
|August 19, 2003|
|Sandy comes to Ryan's rescue once again. Kirsten decides to invite Dawn to an elite Casino Night, but her drinking gets out of control, disappointing Ryan. Dawn believes Ryan is better off with the Cohen's, leaving him with Sandy and Kirsten.|
|The Debut||1.04|| Allan Heinberg|
|August 26, 2003|
|Now that Ryan is staying with the Cohens, he must attend the Cotillion Ball, where Newport's finest young ladies enter society. Luke's jealousy results in Ryan escorting Marissa. Jimmy becomes a suspect of a fraud investigation and Holly's dad decides to confront him at the Ball in front of everyone.|
|The Outsider||1.05||Jesús Salvador Treviño||September 2, 2003|
|Ryan gets a job and meets Donnie, a Newport teen from Corona. Seth decides to invite Donnie to Holly's beach party, but his attendance brings Luke to the hospital.|
|The Girlfriend||1.06||Steven Robman||September 9, 2003|
|Kirsten's father, Caleb Nichol, comes to town with his new 24 year-old girlfried, Gabrielle. Marissa isn't ready to pick between Luke and Ryan, but when she walks in on Ryan with Gabrielle, she chooses Luke. Summer's feelings for Seth begin to show. Julie tells Jimmy she wants a divorce.|
|The Escape||1.07||Steven Robman||September 16, 2003|
|Marissa doesn't take her parents' divorce well, and when she finds Luke with Holly in Tijuana, she's found passed out in an alley. Kirsten, upset that Sandy is considering the job, finds herself in a compromising position with Jimmy in his new apartment.|
|The Rescue||1.08||Josh Schwartz||October 29, 2003|
|Julie blames Ryan for Marissa's incident and tells him to stay away. Sandy starts his new job, and Kirsten is displeased with his new coworker, Rachel. Ryan must take a placement test to determine his enrollment at Harbor. Julie tries to get Marissa to see a therapist in San Diego, contrary to what Jimmy and Marissa want.|
|The Heights||1.09||Josh Schwartz||November 5, 2003|
|Ryan doesn't feel like he belongs at Harbor and Luke doesn't help his situation. Summer keeps her friendship with Seth private, but is jealous of his relationship with Anna. Sandy accepts a case against Caleb at his new job, that will test his relationship with Kirsten.|
|The Perfect Couple||1.10||Josh Schwartz||November 12, 2003|
|Kirsten becomes worried about Sandy's professional relationship with Rachel. Ryan spots Caleb and Julie together, and becomes responsible for Marissa outing their private relationship at a charity event. Summer tells Seth how she feels.|
|The Homecoming||1.11||Josh Schwartz||November 19, 2003|
|Ryan and Marissa go to Chino to visit Trey for Thanksgiving, but he asks Ryan for a favor. Seth must choose between Anna and Summer. Kirsten and Sandy make an attempt to set up Jimmy and Rachel.|
|The Secret||1.12||Josh Schwartz||November 26, 2003|
|Ryan's trust is put to the test when he and Luke spot Carson with another man. Seth struggles to reconcile with Anna and Summer. Caleb and Julie agree to separate for a while. Jimmy and Sandy go into business together.|
|The Best Chrismukkah Ever||1.13||Josh Schwartz||December 3, 2003|
|Kirsten learns something about her father that'll help Sandy's case, but will put her job in jeopardy. Ryan's Christmas does not go as planned. Marissa meets someone in therapy. Meanwhile, Seth struggles choosing between Anna and Summer.|
|The Countdown||1.14||Josh Schwartz||December 17, 2003|
|Kirsten's sister, Hailey, crashes at the Cohen's home and throws a New Year's Eve party that gets out of control. Ryan is worried about Marissa's relationship with Oliver. Anna decides to spend her night with Seth, without Summer's knowledge.|
|The Third Wheel||1.15||Josh Schwartz||January 7, 2004|
|Hailey realizes she is no longer welcome at the Cohen residence. Oliver invites the gang to a Rooney concert, but Ryan catches him in a drug deal in the parking lot. Seth has difficulties telling Summer about his relationship with Anna.|
|The Links||1.16||Josh Schwartz||January 7, 2004|
|Oliver's friendship with Marissa strains her relationship with Ryan. Summer becomes jealous of Seth and Anna's relationship. Meanwhile, Hailey and Kirsten clash when Kirsten convinces Caleb to cut her off.|
|The Rivals||1.17||Josh Schwartz||January 21, 2004|
|Oliver transfers to Harbor, while Ryan risks his academic future to expose him. Seth becomes jealous of Summer's relationship with Danny, forcing him to doubt his relationship with Anna. Meanwhile, Jimmy and Sandy go into business together. Also, Kirsten gets worried about the company when Caleb hires Julie as an interior designer.|
|The Truth||1.18||Josh Schwartz||February 11, 2004|
|Luke starts to see Oliver's true colors after he gets Ryan suspended, but Marissa won't see it. Anna confronts Seth about his relationship with Summer. Meanwhile, Caleb gets Kirsten to break up with Julie for him.|
|The Heartbreak||1.19||Josh Schwartz||February 18, 2004|
|Ryan and Marissa need to rebuild trust after the incident with Oliver, but it's hard when Theresa comes to town. Jimmy discovers he has a secret admirer, while Luke spends the night with Julie. Meanwhile, Seth and Sandy have "the talk".|
|The Telenovela||1.20||Josh Schwartz||February 25, 2004|
|Ryan realizes Theresa isn't telling him the truth on why she's staying in Newport. Summer keeps her relationship with Seth private, turning him to Anna for support. Meanwhile, Sandy finds himself in the middle of Caleb's mess. Also, Jimmy suspects something between Julie and Luke.|
|The Goodbye Girl||1.21||Josh Schwartz||March 3, 2004|
|Seth feels guilty when Anna announces she's moving back to Pittsburgh. Legal troubles brew for Caleb and Kirsten, while Sandy works to solve them. Luke and Julie find their secret affair harder to maintain. Meanwhile, Theresa's boyfriend from Chino arrives bringing trouble.|
|The L.A.||1.22||Josh Schwartz||March 24, 2004|
|Ryan, Marissa, Seth and Summer head down to L.A. and find Hailey working as a stripper. Jimmy and Sandy approach Caleb for business help. Meanwhile, Ryan tries to keep Luke and Julie's affair a secret from Marissa.|
|The Nana||1.23||Josh Schwartz||March 31, 2004|
|Sandy's mother from Florida comes to Newport for a visit with a different attitude. Ryan searches for Marissa. Summer tries to impress Nana. Jimmy and Hailey take a step forward with their newfound romance.|
|The Proposal||1.24||Josh Schwartz||April 14, 2004|
|Marissa doesn't want to hear what Luke has to say, but gives him a chance after a near-fatal car accident. Meanwhile, Jimmy becomes an obstacle in getting a liquor license. Caleb proposes to Julie.|
|The Shower||1.25||Josh Schwartz||April 21, 2004|
|Kirsten and Marissa throw a bridal shower for Julie, but Marissa invites Julie's unwanted estranged sister. Theresa calls Sandy for legal advice, but tries to avoid Ryan. Hailey and Jimmy continue their romance. Meanwhile, Summer is disappointed when Seth meets her father.|
|The Strip||1.26||Josh Schwartz||April 28, 2004|
|While the boys are in Las Vegas, Jimmy and Sandy learn Caleb's true motives. Hailey devises a plan in an attempt to get Caleb to break it off with Julie. Marissa spends the night with Theresa and discovers something that might affect her.|
|The Ties That Bind||1.27||Josh Schwartz||May 5, 2004|
|Caleb and Julie officially get married, and Marissa moves in with them. Ryan and Theresa face a difficult decision regarding her pregnancy. Seth makes a bold move when things around him start to fall apart.|