Objective: To investigate the diagnosis and treatment of primary thyroid malignant lymphoma (PTML). Methods: The clinical data of 23 patients with PTML admitted from January 2000 to December 2011 were retrospectively analyzed. Results: All patients had a history of a rapidly growing thyroid mass. Sixteen PTML cases had markedly high titers of anti-thyroid peroxidase antibody (TPOAb) and/or increased antithyroglobulin antibody (TGAb). Preoperative CT scan revealed that the mass was of lower density than the normal glandular and adjacent muscular tissues, and showed no evident enhancement on the contrast-enhanced scan. Of the entire group, 17 cases underwent radical resection and 6 cases had palliative operation. Eighteen patients received adjuvant chemotherapy (CHOP or COP regimen) and 5 patients underwent radiotherapy. The clinical stages were stage IE in 5 cases, IIE in 17 cases and IIIES in one case, respectively. Fourteen cases were diffuse large B cell lymphoma (DLBCL) and 9 cases were mucosa-associated lymphoid tissue (MALT) lymphoma with regard to the pathological classification. During the follow-up up to January 2012, 17 patients survived for periods from less than one year to more than 5 years. Conclusion: The rapidly enlarging thyroid mass in a background of Hashimoto’s thyroiditis combined with the characteristic CT findings may tend to support the preoperative diagnosis of PTML. Surgical resection and postoperative radiotherapy or chemotherapy are the treatment modalities for this condition.