Online education has become an integral part of higher education with the ever-increasing demand for online doctoral programs. The purpose of this mixed-method study was to explore the nature of student success and contributing factors to improving student success for nontraditional students in an online doctoral program. Relationships between students' grittiness, Big Five personality traits, and their success were explored. Purposeful sampling was used to recruit 136 doctoral alumni, faculty, and administrators. The findings indicated nature of student success is defined by the completion of a degree and professional advancement by enhancement of personal and program qualities, relationship with faculty, soft, technical, social skills, and social support. Students' grittiness, but not their personality traits, was correlated with the length of completing their studies. A student success model was developed with student grit, program-student goal alignment, and a supportive program structure. The findings help to improve doctoral programs and student success.