Background <p>To evaluate the characteristics and treatment outcomes for presumed unilateral congenital superior oblique palsy (SOP) in adults.</p> Methods <p>Retrospective medical records of adult patients diagnosed with presumed unilateral congenital SOP were included. Presumed unilateral congenital SOP was defined as manifesting vertical diplopia and/or head tilt with an insidious or subacute onset or duration of over one year, vertical misalignment greater than 10 prism diopters (PD) and a positive Bielschowsky head tilt test, and/or underaction of the superior oblique (SO) muscle or overaction of its antagonistic inferior oblique muscle on the affected side. The clinical manifestations and surgical treatment outcomes of presumed congenital SOP in adults were evaluated.</p> Results <p>Among adult patients initially diagnosed with unilateral SOP, 41% were classified as presumed congenital SOP. Patients exhibited various clinical manifestations beyond the typical over-elevation or under-depression during adduction, with the greatest deviation in the field of action of the SO muscle observed in only 6.9% of cases. Orbital imaging revealed SO asymmetry due to the SO hypoplasia in 58.5% of patients. Among various factors, combined horizontal strabismus was more common in those with symmetric SO, with no significant differences in clinical presentation or surgical outcomes based on SO volume. The overall surgical outcome for presumed congenital SOP was generally favorable, with an 85% success rate. No factors including the presence of SO hypoplasia influenced the surgical result.</p> Conclusions <p>In adults with presumed congenital SOP, diverse clinical manifestations were observed. The angle of deviation, duction and version patterns, and treatment outcomes were not associated with the presence of SO hypoplasia on MRI. Despite the diversity in clinical features, treatment outcomes remained favorable.</p> Trial registration <p>Retrospectively registered.</p>