Beverly Marsh is one of the seven members of The Losers' Club. She is sexually abused by her father, Alvin Marsh, and bullied by Gretta Keene and some of the other students at school because of rumors of her being promiscuous. She is best friends with Bill Denbrough, Richie Tozier, Eddie Kaspbrak, Stan Uris, Ben Hanscom, and Mike Hanlon. Beverly also has a crush on Bill.
In the book she’s described as a really pretty girl with auburn hair that reaches her shoulder blades, lovely gray-green eyes and milky skin with a spray of freckles. In the 1990 mini-series, she has chest-length brunette hair and in the 2017 film adaption, she has red hair.
Beverly is known to be very insecure, due to her uneasy life at home because of her father's abusive nature, and being picked on at school most of the time. Nonetheless, she is very good-hearted.
While Beverly is in the girls’ bathroom, Gretta Keene bursts in and bullies her. Another girl pulls the trash bag out of the trash can, and proceeds to dump its contents on Beverly’s head; Beverly immediately holds her backpack above her head for protection. As Ben is getting his bike, Beverly steps outside and talks with him, telling him that Henry Bowers and his cronies are by the west entrance. She jokes around with him before introducing herself and signing his yearbook.
While Bill, Eddie, and Stan are in Mr. Keene's pharmacy collecting supplies to help Ben recover from his injuries that Bowers caused, Beverly is also in the pharmacy, and comes into their aisle to avoid Gretta. They explain their situation to her, and she distracts Mr. Keene long enough for the three to sneak out with their supplies. As Eddie is attending to Ben's wound, Beverly turns up again, and Bill invites her to go to the quarry.
Returning home, her father, Alvin, confronts her, and gets hands-on with her. Disgusted, Beverly goes into the bathroom and cuts her hair. The next day, as Bill, Eddie, Ben, Stan, and Richie are at the edge of a cliff overlooking a lake, Beverly shows up and jumps off the cliff, much to the boys' disbelief. After the six go for a swim, Beverly sunbathes; Stan, Richie, Ben, Bill, and Eddie can't help but look at her, and turn away when she looks toward them, and joins them as they look at Ben's history of Derry. They then go to Ben's house, where he shows them more of the town's history, and Beverly exposes Ben's interest in the New Kids on the Block.
That evening, Beverly finds a postcard from Ben in her backpack, and goes into the bathroom to read it, feeling good that someone has a thing for her. She then hears voices coming from inside the sink. Going downstairs into the den where her father is sleeping to grab a tape measure, she puts it into the drain as far as it can go; pulling it back up, it comes out covered in blood. Without warning, tendrils grab Beverly's wrists, and then wrap themselves around her face, pulling the shrieking girl closer to the drain. Suddenly, blood shoots out of the sink, right in Beverly's face and all over the bathroom. Whimpering, sobbing, and screaming, Beverly backs away from the sink over to the bathtub. Her father, obviously awakened by her shrieking, enters the bathroom, but doesn't see the blood all over the bathroom, and is surprised to see that Beverly cut her hair.
After the events of the summer of 1989, Beverly has grown up and become a fashion designer in Chicago, while having gone through numerous abusive relationships over the years, including her marriage to Tom Rogan, who considers her a sex object. When she gets word that Pennywise is causing trouble around Derry again, she, Ben, Bill, and Eddie return to their childhood home town to eliminate the creep as promised.
- The 2017 remake implies Beverly had recently experienced her first period. Given she was looking at tampons at the drug store.
- In the novel, she is described by Stephen King having red or auburn hair, but in the 1990 miniseries, she has brown hair while in the 2017 film, she is a redhead.
- She is both the love interest of Bill and Ben who both kiss her in the 2017 film.
- She uses a slingshot to defeat It in the novel and in the miniseries but in the 2017 film, she beats It up and impales him with a rebar.