DeBues-Stafford enjoyed a strong 2019, breaking the national records for the indoor mile and 5,000 metres, and the outdoor 1,500 metre, mile and 5,000 metre records. She would go on to add the indoor 1,500 metre record in 2020. Making her second Worlds appearance at the 2019 World Athletics Championships in Doha, she advanced to the final in the women's 1500 m event and placed sixth with a time of 3:56.12. In doing so she achieved her previously-stated goal of running in the final in a time under four minutes. She remarked afterward that "I really believed I had a chance at a medal, even 200 meters from the finish," but that "once I was into the homestretch, I knew I didn’t have it." Following this, she moved to train at Portland's Bowerman Track Club under Shalane Flanagan.