Moideen founded Thumbay Group in 1998. The group operates across 20 sectors, including healthcare, medical research, and pharmacy. It operates the Thumbay University Hospital, Thumbay Hospital, Thumbay Medical & Dental Specialty Centre, Thumbay Hospital Day Care Chain, and the Thumbay Dental Hospital located in Thumbay Medicity. Moideen also founded educational establishments, including the Gulf Medical University. In December 2022, Thumbay Labs and Thumbay University Hospital launched 19 short-term online programs and the Centre of Excellence for Bones and Joints, respectively.