Objectives To evaluate the association of Graves' Ophthalmopathy (GO) with the meibomian glands and investigate the relation of ocular surface changes with meibomian gland parameters in patients with GO. Methods This prospective study included 44 eyes of 44 mild and moderate-to-severe GO patients and 38 eyes of 38 control subjects. After a complete ophthalmologic examination, patients were assessed according to the Clinical Activity Score (CAS). The area of meibomian gland loss and meibography score was evaluated using meibography (Sirius; CSO, Florence, Italy). Schirmer test, tear break-up time (TBUT) and Ocular Surface Disease Index (OSDI) scores were evaluated. Results Mean meibomian gland dropout area was 26.29 +/- 1.58% in the GO group and 14.46 +/- 1.52% in the healthy controls (p < .001). Mean meibography score in the GO group was 2.61 +/- 0.15 while it was 1.32 +/- 0.25 in the healthy controls (p < .001). Meibomian gland dropout area was positively correlated with CAS and OSDI questionnaire results (p = .015, r = 0.391; p < .001, r = 0.662, respectively) and negatively correlated with TBUT and Schirmer test scores (p < .001, r = -0.635; p = .003, r = -0.474, respectively). Meibography score was positively correlated with CAS and OSDI questionnaire results (p = .012, r = 0.383; p = .007, r = 0.419, respectively) and negatively correlated with TBUT and Schirmer test scores (p = .002, r = -0.467; p = .023, r = -0.359, respectively). Conclusion Meibomian glands are quantitatively decreased in patients with GO. The decrease of meibomian glands is correlated with objective and subjective dry eye findings. Dry eye treatment in GO patients should include meibomian gland deficiency as well.