The Wilson family arrives in Beverly Hills, after Harrison "Harry" Wilson takes a job as the principal at West Beverly High School, while his children, Annie and Dixon, attend the school during their first week much to the awkward circumstances of their father watching over them, while Harry and his photographer wife, Debbie, also keep a close eye on Harry's washed-up, alcoholic, actress mother, Tabitha. For Annie and Dixon, the school is one big culture shock for Annie, a sweet and friendly girl with a passion for the theater, and Dixon, a star athlete and scholar who was adopted by the Wilson family after they took him in as a foster child. Annie and Dixon have a close sibling relationship, which they'll need to help them cope with all the new cliques and classmates, including Naomi Clark, a hot and stereotypical spoiled rich girl who believes that money buys everything; Ethan Ward, Annie's former boyfriend from Kansas who's now Naomi's boyfriend, and a popular lacrosse star whose abilities rival Dixon's; Navid Shirazi, an aspiring student reporter who heads up the school's daily TV newscast; and Erin Silver, a rebel and wanna-be socialite who produces and stars in a YouTube-type video series, and who develops a crush on Dixon. Adrianna is a fellow student and theater "goddess" who is Naomi Clark's best friend... and Ethan Ward's secret girlfriend, and who has a serious drug addiction; George Evans is an arrogant West Beverly High student, who takes an instant dislike to Dixon because of his race (Dixon is black). Wendy is "sexy vixen" student at West Beverly Hills High who takes every advantage of her looks; Ty Collins is another student and theater major. Even the faculty seems hip and sophisticated at the school whom include the smart and funny teacher Ryan Matthews, beautiful guidance counselor Kelly Taylor, and successful theater actress-turned-high school-musical director Brenda Walsh. The Wilson family has just begun to realize how much their lives are about to change.

Naomi finds herself in trouble when she fails an assignment, and Ryan and Kelly bring the issue to Harry's attention, while Harry struggles with a disturbing revelation about the result of a secret tryst with Naomi's mother, Tracy, from many years ago. Meanwhile, Dixon learns more about Navid when they team up to try to pull a school prank against Palisades High. Annie meets a potential love interest in the form of drama student Ty Collins, who turns out to be the wealthiest student at West Beverly, and who spirits her away for San Francisco for the evening. Silver posts the story about Ethan's infidelity with Naomi on her Internet blog, while Adrianna continues her self-destructive slide into drugs and debauchery. Also, Ryan tries to ask Kelly out on a date, but she has to find a babysitter first for her four-year-old son, and former West Beverly alumni Brenda Walsh, now a successful Broadway and London theater director, arrives back in town to help put on a new school play.

As Silver's "half birthday" approaches, she decides to spend a spooky evening by watching horror movies with her friends at the famous Hollywood Forever Cemetery. But Dixon is not eager to attend when he reveals to her that he does not watch horror films. Meanwhile, Harry's past returns to haunt him when Tracy reveals she is searching for their long-lost illegitimate son. Annie and Ethan are paired up for an assignment, which leads to a possible romantic connection after the two take care of a baby. A mysterious new student, named Kimberly MacIntyre, arrives at West Beverly which considers with a police raid on the school searching for narcotics which leads Naomi to cover for Adrianna when Naomi takes the fall by taking her cocaine stash. After Naomi confronts Adrianna over her escalating drug addiction, she agrees to come forward to clear Naomi, but Adrianna soon goes back on her word when she lands another acting role which could jump-start her acting career and make her difficult-to-please mother proud. Also, Ryan seeks to explore his horizons since his breakup with Kelly by dating an attractive, but dim-witted actress.

Silver invites a few of her female friends over at her house for a girls' night, but the event quickly turns into a house party which causes massive damage to hers and Kelly's house. Meanwhile, Debbie and Harry finally reveal to Dixon and Annie that they have a long-lost, out-of-wedlock brother who was given up for adoption by Tracy Clark over 20 years ago. Dixon, who does not appear upset by the news, deals with the situation by talking to Silver about it. However, the news bothers Annie and she takes out her anger and frustration at Silver's party by getting drunk and being insulting to everyone. Annie and Ethan decide to keep their relationship a secret, while Naomi continues to hang out with the trouble-making Ozzie. Elsewhere, Adrianna and Navid continue to grow close until they have a misunderstanding. Also, a student sees Ryan and Kimberly kissing and begins to make demands to Ryan, while Kimberly is just determined to keep her secret identity under wraps at any cost and informs Harry about what's transpired between them.

Kelly arrives back in Beverly Hills and reveals to Silver what happened between her and Dylan during her trip. She also confronts Ryan, who has taken a leave of absence, about the rumors that he hooked up with a student, while Ryan refuses to explain his actions to Kelly or anyone else as not to jeopardize Kimberly's undercover status to nail the drug pushers at West Beverly. On Annie's 16th birthday, Naomi sees her kissing Ethan and decides to get back at her by inviting Annie's old boyfriend, Jason, to her birthday party hoping it will break up her and Ethan, who continue to debate over keeping their blossoming romance a secret... unaware that everyone around them already knows. Meanwhile, Adrianna has dinner with Navid and his large Iranian family and she also finds out that Navid is a virgin. At the end, the big twist comes when Harry's 22-year-old illegitimate son, Sean, visits the Wilson family for the first time during Annie's party.

Adrianna reveals the secret that she's pregnant individually to both Naomi and Navid, who handle the news differently than expected. When Dixon reveals the depths of his feelings to Silver, their relationship takes a surprising turn when she reveals some facts about herself and that of her feelings of love. Meanwhile, Tabitha surprises Annie and Dixon with an unexpected belated Christmas gift of a car: which both Debbie and Harry disapprove of Tabitha trying to buy her grandchildren's affection after she also announces that she is leaving town to re-start her acting career with a job on a TV soap opera in New York. With a massive heat wave hitting the L.A. area, Annie and Ethan decide to to take a day-long escape to Tabitha's house Palm Springs for a romantic time alone.