Women with endometriosis may experience uncertainty owing to the characteristics of the disease, including vague symptom patterns, delayed diagnosis, and long-term management with no cure. However, women use various coping strategies to adapt to the uncertainty caused by their endometriosis. This descriptive qualitative study explored the coping experiences of women with endometriosis to reduce their uncertainty about the disease and to achieve successful adaptation to their lives with endometriosis. By using convenience and purposive sampling methods, qualitative data were collected from 14 women in South Korea (mean age = 37.7 years, age range = 27–54 years), who were diagnosed with endometriosis through laparoscopy or open surgery. All interview data were thematically analyzed. Four themes were identified as adaptive coping experiences: (1) gaining self-control over the ambiguous disease; (2) regaining the daily routines destroyed by the disease; (3) being emotionally supported and expressing oneself when feeling unsupported by society; and (4) taking an active role in one's treatment plan by being self-directed. Patients' sense of self-control and self-directedness regarding the disease and the treatment process were important to adapt to life with endometriosis. In addition, regaining stable daily routines as well as being emotionally supported were critical for decreasing their uncertainty. This paper has widespread implications, including the need for training or a continuing education program for health professionals to enhance their competencies when caring for women with endometriosis and the need for social efforts to increase awareness of the disease.