Objectives Radioiodine can be applied for remnant ablation in low and low to intermediate-risk patients with differentiated thyroid cancer (DTC). A controversy still exists about the application time interval of radioiodine following total thyroidectomy. In this study, we investigated the effect of radioiodine (RAI) therapy timing on the success rates of the ablation. Methods We retrospectively reviewed the data of DTC patients who underwent total thyroidectomy and were treated with radioiodine remnant ablation during 2013-2017. Because the objective of this study was to determine the success of ablation according to the postoperative RAI therapy timing, any patients with a pathologic uptake outside the thyroid bed as well as high-risk patients determined before and at RAI therapy were excluded from the study. Finally, 503 patients with low and low to intermediate-risk groups were included in the study. Successful ablation was defined as no visible focal uptake on the neck on I-131 whole body scan with stimulated thyroglobulin (Tg) level of < 1 ng/mL and a normal or undetectable antithyroglobulin antibody (ATG). The time interval from total thyroidectomy to RAI therapy (titRAI) was calculated as months for each patient. Results A total of 115 (22.9%) patients were in the low to intermediate-risk group whereas most of the patients were at the low-risk group according to the American Thyroid Association (ATA) 2015. Successful ablation was observed in 388 (77.1%) patients. The titRAI was <= 3 months in 151 (30.0%) patients and > 3 months in 352 (70.0%) patients. The ratio of successful ablation was statistically higher in patients with a titRAI > 3 months (81.2% of patients) than in patients with <= 3 months (67.5% of patients) (chi(2) 11.247, p 0.001). The rate of successful ablation was 20.3% higher in patients treated after 3 months. There was no statistical difference when titRAI cut off was reduced to 2 months (p > 0.5). Conclusion Investigated the effect of radioiodine therapy initiated before 3 months after total thyroidectomy and it seems to decrease ablation success.