In 1908, she became co-founder of the National Association of Colored Graduate Nurses (NACGN). This association did not discriminate against anyone and aimed to support and congratulate the accomplishments of all outstanding nurses, and to eliminate racial discrimination in the nursing community. The association also strived to commemorate minority nurses on their accomplishments in the registered nursing field. In 1909, Mahoney spoke at the NACGN's first annual convention, which became the first time that Martha Minerva Franklin and Adah Belle Samuels Thoms met Mahoney in person. The NACGN struggled in their early stages with only 26 female nurses in attendance of their first national convention. In her speech, she recognized the inequalities in her nursing education, and in nursing education of the day. The NACGN members gave Mahoney a lifetime membership in the association and a position as the organization's chaplain.