In 1947, Abramson joined with Ahmet Ertegun to form Atlantic Records, and Miriam took charge of the fledgling company's finances and production, handling payments to musicians and negotiating distribution deals.

A profile of her in Billboard that year, headlined "Atlantic's 'Money Man' Is a Woman,” described her as "one of the few women executives in the record industry, a business heretofore noted for its lack of fem talent."

She ran the company office and developed a reputation for toughness, later stating: "If the distributors didn't pay their bills, I was very nasty.

She also had very good taste in music.”[6] Although some musicians were critical of the level of royalties they received through her, she said: "We didn't try to cheat anybody, and what we did was normal practice at the time.

She also produced a play, Strider, that ran on Broadway in 1979-1980 and invested in the 2014 musical Beautiful, based on the work of Carole King.