BACKGROUND Lymphomas are the second most common malignancy of the head and neck. In this region, the vast majority of extranodal lymphomas are located in the palatine tonsil, accounting for about 51%. Tonsillar lymphomas are aggressive tumors with intermediate- or high-grade histology. We here report a case of primary non-Hodgkin's lymphoma of the palatine tonsil and analyze its ultrasound features. CASE SUMMARY A 40-year-old man presented with right palatine tonsil swelling for 2 mo after a cold, accompanied by dysphagia, snoring, and suffocation. He had no sore throat, fever, or history of upper respiratory tract infection or tuberculosis. The patient was generally in good health and denied other diseases. He was diagnosed with acute tonsillitis initially and treated with antibiotics for 7 d. However, there was no improvement with the treatment. Tonsil biopsy and ultrasound-guided biopsy of the biggest lymph node of the right neck showed the typical pathology of non-Hodgkin lymphoma. CONCLUSION Primary lymphoma of the tonsils is rare, and its diagnosis is challenging. Ultrasound is a useful modality in diagnosing oropharyngeal diseases, and can clearly show the features of this tumor, but the final diagnosis should be established by histology.