Background and Objectives: Following the initial management, some patients with differentiated thyroid cancer (DTC) develop a state of high thyroglobulin (Tg) and Negative Iodine Scintigraphy. The predisposing factors and outcome of this condition are unclear. In this study, our objectives were to analyze the characteristics of patients with high Tg level and negative Iodine scintigraphy and to determine the predictive factors for development of high Tg and negative scintigraphy. Patients and Methods: Retrospective study of 34 patients undergoing treatment for DTC, followed in the Nuclear Medicine department of the University Hospital—Sahloul Sousse between 1990 and 2006 and having a high Tg and negative Iodine scintigraphy. Fourteen patients had Tg between 2 and 10 ng/ml, 16 had Tg between 11 and 100 ng/ml and 4 patients had Tg more than 100 ng/ml. Results: There were 25 women and 9 men. The mean age was 51.65 years. In 94.1% of cases, the tumor was papillary carcinoma. Follicular tumors accounted for only 5.9%. The mean nodule size was3.26 cm. Capsular invasion was seen in 47.1% cases. The locoregional invasion was found in 35.3%. The lymph node extension was found in 84.8% of patients having lymph node surgery. Lymph node involvement was observed in 92.8% of patients with papillary cancer but it was found in 7.2% of patients with follicular cancers. Lymph node invasion was unilateral in 28.6% (N1a) and bilateral, contralateral or mediastinal in 71.4% (N1b). Initial level of Tg was as follows: 7 patients had Tg between 2 and 10 ng/ml, 14 patients had Tg between 11 and 100 ng/ml and 12 had Tg more than 100 ng/ml. The mean number of radioactive Iodine cure was 11.08 for patients with Tg more than 100 ng/ml with a significant difference (P = 0.001). Conclusion: Among epidemiological, pathological and clinical characteristics, lymph node invasion is the most frequent parameter found in patients with a DTC with high Tg level and negative Iodine scintigraphy.