Mariah Bell was born on April 18, 1996 in Tulsa, Oklahoma. She is the second child of Kendra and Andy Bell. Her older sister, Morgan, has skated with Disney on Ice.
At age 12, Bell moved with her mother and sister from Houston to Westminster, Colorado. She graduated from Ralston Valley High School in 2014, and was named the school's Super Senior. She rides the unicycle to help with her balance and core strength.
Bell began skating at the age of four because of her sister. Early in her career, she was coached by Megan Faulkner, Billy Schneider, and Candy Brown. At age 12, she joined Cindy Sullivan in Westminster, Colorado.
At the 2012 U.S. Championships, Bell finished 5th in the junior division. She was assigned to the 2012 Gardena Spring Trophy and won the junior silver medal.
Bell won the silver medal in the junior division of the 2013 U.S. Championships, behind Polina Edmunds.
During the 2013–14 season, Bell was coached by Cindy Sullivan in Westminster, Colorado. Making her ISU Junior Grand Prix debut, she won a bronze medal in Mexico and finished 7th in Poland. At the 2014 U.S. Championships, Bell finished 13th. Soon after her high school graduation in 2014, she moved to Monument, Colorado, so that she could train under Kori Ade.
Bell's senior international debut came in the 2014–15 season. She competed at two ISU Challenger Series events, the 2014 Nebelhorn Trophy where she finished fifth, and the 2014 Golden Spin of Zagreb where she placed eighth. She finished 6th at the 2015 U.S. Championships, having ranked 12th in the short program and 6th in the free skate.
In 2015–16, Bell started her season on the ISU Challenger Series (CS), placing 6th at the 2015 U.S. International Classic and 13th at the 2015 Ondrej Nepela Trophy.
Making her Grand Prix debut, Bell finished 8th at 2015 Skate America, scoring personal bests in the free skate and combined total score. She placed 11th at the 2016 U.S. Championships.
Bell changed coaches in August 2016, joining Rafael Arutyunyan in Lakewood, California. She landed on the podium at two of her 2016–17 ISU Challenger Series assignments. Ranked second in both segments, she took silver at the 2016 CS U.S. International Classic, behind Satoko Miyahara. At the 2016 CS Ondrej Nepela Memorial, she placed fifth in the short, fourth in the free, and third overall behind Maria Sotskova and Yulia Lipnitskaya. She was invited to the 2016 Skate America to replace the injured Angela Wang. She won the silver medal behind Ashley Wagner after placing sixth in the short program and first in the free skate.
In January 2017, Bell received the bronze medal at the U.S. Championships, earning her a spot on the Four Continents and World teams. In February, she placed 6th at the 2017 Four Continents Championships in Gangneung, South Korea. She later placed 12th at her first trip to the 2017 World Championships in Helsinki, Finland.
GP: Grand Prix; CS: Challenger Series; JGP: Junior Grand Prix