The aim of this study was to determine the clinical and immunological characteristics of older adults with common variable immunodeficiency (CVID). Patients aged ≥18 years who were followed up with the diagnosis of CVID between 2015 and 2020 were included in the study. The patients were separated into two age groups according to the age at diagnosis: the adult group, aged 18-65 years (n=49) and the older adult group, aged ≥65 years (n=11). Splenomegaly (55.1% vs. 9.1%, p=0.006), bronchiectasis (53.0% vs. 9.1%, p=0.008), and autoimmunity (42.8% vs. 9.1%, p=0.036) were determined to be more common in the adult group than in the older adults. A similar frequency of malignancy was seen in both groups (6.1% vs. 9.1%, p=0.721). There were significantly more patients with no comorbidity in the older adult group than in the adult group (45.5% vs. 16.3%, p=0.034). Serum IgG and IgA levels were determined to be significantly higher in the older adult group than in the adult group (p=0.001 for all). The CD19+ B-cell count at the time of diagnosis was determined to be lower and the CD19+CD27+IgD- switched memory B-cells and CD16+CD56+ natural killer cell counts were higher in the older adults than in the adult group (p=0.016, p=0.032, p=0.044, respectively). Knowledge of clinical and immunological differences in older adult CVID patients may be of benefit in polyclinic follow-up and in respect of changes to be made to the treatment plan.