Paranasal sinus mucoceles (PSMs) can involve the orbit because the topographic anatomies of the paranasal sinuses and orbit are interrelated. We encountered 27 patients with PSMs involving the orbit that caused orbital symptoms. In this study, we evaluated the frequent symptoms and signs of PSMs involving the orbit, and report postoperative changes of orbital symptoms including the effects on visual acuity. A retrospective chart review, radiologic evaluation, and interviews were conducted after Institutional Review Board approval was obtained. Over the past 11 years, we encountered 27 patients with PSMs involving the orbit. We classified the patients according to orbital symptoms and PSM origin, and evaluated the surgical outcomes. A total of 27 patients (17 males and 10 females) with PSMs involving the orbit were included in the present study. The mean patient age was 51.0 ± 9.7 years (range 32-90) and the mean follow-up period was 20.5 months (range 2-84). Proptosis (15/27, 56%) was the most common symptom. Other common symptoms included orbital pain (9/27, 33%), decreased visual acuity or vision loss (9/27, 33%), and diplopia (7/27, 26%). All symptoms except for vision loss were improved by endoscopic marsupialization regardless of the disease period. Four out of five patients with decreased visual acuity experienced complete recovery. The remaining patient showed partial improvement after surgery. Four patients who were blind when they initially visited the hospital did not show any improvement after surgery. For PSM patients with decreased visual acuity, we can predict that vision will improve after surgery regardless of the disease duration. However, blindness will probably not resolve after endoscopic marsupialization. Even if the orbital symptoms (except for blindness) have persisted for a long time, surgery could still produce positive outcomes.