Objectives To explore the degree to which patients undergoing unilateral endoscopic sinus surgery (ESS) experience post-operative contralateral sinonasal symptoms and determine risk factors for contralateral symptomatology following unilateral ESS. Methods Patients who underwent unilateral surgery for chronic rhinosinusitis (CRS) were contacted and asked if they felt symptomatic on the contralateral side at that point in time. Nasal Obstruction Symptom Evaluation (NOSE) scores were obtained based on contralateral symptomatology they recalled at the following time points: pre-ESS, 1 month post-ESS, and 3 months post-ESS. Demographics, contralateral symptomatology, and NOSE scores were compared between those with 2 or fewer sinusotomies versus 3 or more sinusotomies. Results Of the 97 patients included in this study, 24% of patients reported contralateral congestion, a median of 24 months post-ESS, and more than 10% of patients reported other contralateral symptoms including swelling, rhinorrhea, difficulty breathing, and hyposmia post-ESS. Those with 2 or fewer sinusotomies were more likely to feel that they had developed worsened sensation of contralateral sinus swelling ( P = .008). The median amount of time from the participants’ index surgery until the time they were interviewed was 24 months. There were no differences in long-term contralateral symptomatology between those who did and did not have septoplasty (27%). Conclusion Patients who have unilateral ESS for CRS may experience long-term contralateral symptoms. Having a septoplasty did not affect contralateral symptoms.