AbstractImportanceTo investigate the choroidal thickness (CT) in patients with thyroid‐associated orbitopathy (TAO).BackgroundTo compare CT of TAO patients and healthy subjects.DesignProspective cross‐sectional study in a public hospital.ParticipantsOne hundred and four eyes of 52 TAO patients and 52 eyes of 26 healthy subjects.MethodsCT was measured with enhanced‐depth imaging optical coherence tomography (EDI‐OCT) at the subfoveal, macular and peripapillary regions. Multivariate linear regression was used to evaluate the associations of subfoveal CT with systemic and ocular variables among TAO eyes.Main Outcome MeasuresCT of both groups.ResultsCT of eyes with TAO was significantly increased at the subfoveal region, 1 and 2 mm from the fovea nasally, temporally and superiorly, and 1 mm inferior to the fovea (all P < .05). No significant difference was found in CT at 2 mm inferior to the fovea (P = .094) and all four quadrants of the peripapillary region (superior, P = .096; nasal, P = .732; inferior, P = .179; temporal, P = .052). Among TAO eyes, thinner subfoveal choroid was associated with worsening exophthalmos (P = .043), poorer visual acuity (P = .017), increasing age (P = .040) and axial length (P < .001). There was no association between CT and clinical activity score (P = .239).Conclusions and RelevanceTAO patients showed thicker choroid than controls over the macula, but not the peripapillary regions. Thinner subfoveal choroid was associated with worsening exophthalmos and poorer vision. EDI‐OCT can monitor choroidal vascular changes associated with TAO and its complications.