They've always been close friends, but secretly, Betty harbored romantic feelings towards him, leaving their friendship strained as Archie doesn't feel the same way.
After Betty admitted her feelings for Archie, things were complicated between the two, but they were able to return to being friends. Betty and Archie are now best friends, she has gotten over her feelings for Archie, as she's now dating Jughead Jones, while she approved Archie and Veronica Lodge's romantic relationship.
Archie and Betty have been next-door neighbors since they were four years old, and have always been in the same school, grade, and classes together, ever since they could remember. When they were in the second grade, Archie was falling behind in reading and he would have been held back another year. Hating the idea of them being in different grades, Betty tutored Archie every day after school. He was later able to move up a grade with Betty.
Young Archie was so ecstatic that he kissed and proposed to Betty, but she turned him down as they were too young for marriage. However, she told him to ask her when they were eighteen and she would say yes.
The two best friends, Archie and Betty, had a date at Pop's Chock'lit Shoppe where they reunited after spending the summer apart. Whilst Archie told her about his newfound desire to pursue music as a career, Betty hoped to reveal the romantic feelings she harbored for him. However, as she was on the brink of confessing her love for him, when they are distracted by the arrival of a new girl in town — Veronica Lodge. Veronica and her mother Hermione Lodge came to Riverdale from New York to escape the scandal of her father's arrest for fraud and embezzlement. Archie was immediately intrigued by this new arrival, who would be starting at Riverdale High School the next day, and Betty, noticing this, stayed silent about her feelings.
The next day, Veronica, upon hearing of Betty's interest in Archie, encouraged Betty to ask him to the back-to-school dance, but due to her lack of confidence, Betty ended up asking Archie to be her and Veronica's escort to the dance instead. At the Semi-formal, Betty and Archie were on the dance floor, when she confessed how she'd been imagining them as a "power couple". He didn't really give her the reply she was hoping for. This upset Betty that he couldn't even think of them being more than just friends. Archie really did like Betty, but he thought he could never live up to her expectations and believed she was too perfect for him.
Later on, at the after-party, Cheryl Blossom conspired to stir up trouble. She used a game of Spin the Bottle to force Archie and Veronica to play Seven Minutes in Heaven together, knowing it would upset Betty. Though they tried to fight their attraction for each other out of respect for Betty, they ended up kissing. When they returned to the party, Cheryl gleefully informed them that Betty had fled, so Archie went after her. When he arrived at her house, a tearful Betty walks down the narrow path toward him in tears. Betty tearfully asked Archie if he loved her at all, to which Archie replied that he does, but he would never feel worthy enough to date her. Archie eventually told Betty that he "couldn't give her the answer she wants", and Betty finally retreated inside her home, feeling destroyed.
Archie became torn when news got out about Jason Blossom's death by gunshot, as he and Miss Grundy had heard a gunshot when they were together at the Sweetwater shore. However, telling the police about it would mean that Archie would most likely have to tell them about his and Grundy's relationship. He tried to talk to Betty, but exhausted and crestfallen over his rejection, she dismissed him through text. The next morning, despite telling her mother that she would no longer seek friendship from Archie, Betty did the very opposite by asking him to walk her to school. She needed time to process the situation, to separate what she wanted from what her mom wanted, and what she wanted was to be friends with Archie. Betty eventually came around and decided that whether Archie reciprocated her feelings or not, Betty still wanted them to be friends.
However, as the gang gathered at lunch to listen to Archie play one of his songs, Betty reminisced about the events of the weekend, becoming emotional and, unable to hold it together anymore, lashed out at Archie. Archie tried to console her, but Betty once again dismissed him, as her heartbreak was too recent to handle in front of him. Betty resented both Archie for rejecting her feelings and Veronica for kissing him at the party and siding with Archie.
Later, at cheer practice, she and Veronica got into an argument over Archie, her informing Archie of her true feelings towards him, and the awkward tension now between them because of it. To get back at Veronica, Betty invited Cheryl to get manicures with her, but it backfired. At school the next day, Betty admitted that Veronica was right about what she said pertaining to Archie, sometimes it's hard to admit things to yourself, Betty said.
That night at the Pep Rally, Betty was shocked to see Archie's bruised eye after his fight in the student lounge with Reggie. Following the Pep Rally, Betty and Veronica made up and went for smoothies at Pop's. The two were later joined by Archie and Jughead, so Betty invited them to join her and Veronica at the table. 
Once Betty discovered that Archie and Grundy were in a relationship, Betty was alarmed and tried to talk Archie out of it. Betty's suspicion on Ms Grundy made her obsessed with finding out the truth about Ms Grundy's unknown past. Betty’s internet research dug up even more troubling details about Geraldine. There was no record of her life before she moved to Riverdale a year ago. Archie was nevertheless frustrated by Betty’s investigation, insisting she let it go.
Although this did not stop a determined Betty. Later on, Betty, along with Veronica, broke into Miss Grundy's tiny Volkswagen Beetle and found proof of her shady background. They found a box with Miss Grundy's driver's license with the name Jennifer Gibson and a revolver. Archie confronted Geraldine who then told him that she was in a violent, abusive marriage. When she left, she changed her name. He believed her.
When she finally stopped her searching, Alice found the gun inside Betty's drawer. She grabbed for Betty's diary, leading to her, Betty, and Fred confronting Archie and Grundy. Although the confrontation ended with Grundy being run out of town by Alice, Archie was shown to have no ill towards Betty.