Purpose: To investigate changes in Quality of life (QOL) and related factors in patients with thyroid cancer undergoing Radioactive Iodine remnant ablation (RAI). Methods: Data were collected longitudinally 3 times for 6 months (2 weeks post-surgery, post RAI, 3 months post RAI) in a hospital located in Seoul. Questionnaires were used to measure levels of physical symptoms, anxiety, depression, and QOL. Ninety-eight patients with thyroid cancer who had RAI were included in the analysis. Data were analyzed using SPSS (18.0). Results: Findings for the three data collection times respectfully were: mean scores for physical symptoms, 0.53, 1.21 and 0.62, patients with depression, 47%, 36.7% and 37.7%, patients with anxiety, 18.4 %, 19.4% and 20.4%, mean scores for QOL, 7.06, 7.01 and 7.28. QOL score was highest 3 months post RAI (p=.031). In the stepwise multiple regression analysis, depression and fatigue were predicting factors for low QOL at all data collection times. Dysponia was a predicting factor for low QOL post RAI and 3 months post RAI. Conclusion: To increase QOL, it is necessary to provide information in advance regarding physical & psychological symptoms and to develop nursing intervention programs to decrease depression and fatigue.