Objective: To demonstrate the presence of splenomegaly in primary antiphospholipid syndrome (PAPS) patients without accompanying portal hypertension or comorbidity. Methods: Twelve patients (7 women) aged 23–65 years followed upon the diagnosis of PAPS were enrolled in the study. We documented the identified causes of splenomegaly in patients with PAPS, and searched for the potential causes of splenomegaly in patients with spleen enlargement. PAPS patients with or without splenomegaly were evaluated in terms of demographic and clinical findings. Results: Splenomegaly was present in 6 of the 12 patients. In these patients, there were no infections, hematological disorders, portal hypertension or malignancy that might lead to splenomegaly. The long axis of spleen was found to be in the range of 137–155 mm in patients with splenomegaly. Splenomegaly was more frequently determined in female PAPS patients. The splenomegaly group had a longer duration of disease (median 5.5 vs. 0.75 years) and a higher number of thrombotic events (median 3 vs. 1.5). The splenomegaly group was especially composed of patients who never received any anticoagulant and acetylsalicylic acid, or who used these agents irregularly for very short periods. Conclusion: Splenomegaly was observed in association with disease duration, frequency of thrombotic events and irregular antiaggregant or anticoagulant treatment in patients with PAPS, in the absence of comorbidity or portal hypertension.