Aim: Determine if selective laser trabeculoplasty (SLT) affects the fellow eye's intraocular pressure (IOP). Materials and methods: A retrospective review of 76 pairs of eyes from 76 adult glaucoma patients who underwent SLT in one eye with at least 2 months between treatments were evaluated for IOP and medication reduction in the untreated fellow eye. Success was defined as ≥20% IOP reduction or ≥1 medication reduction without any additional IOP lowering procedures or medication. The primary outcome measures were success, IOP, and medication reduction in the untreated fellow eye at 6 months. Results: At 6 months after SLT treatment, 48.7% (38/76) treated eyes and 36.8% (28/76) untreated fellow eyes met success criteria. IOP reduction in the treated eye was 2.6 ± 5.8 (14.1%; p < 0.002) and 0.8 ± 4.3 (5.1%, p = 0.122) in the fellow eye. The fellow eye was significantly more likely to meet success criteria if the treated eye was successful [odds ratio (OR): 6.00, 95% confidence interval (CI) (2.11–17.06), p < 0.002]. Conclusion: After a unilateral treatment with SLT, over one-third of the fellow eyes experienced either ≥20% IOP reduction or medication reduction. Additionally, fellow eyes were six times as likely to meet success criteria if this was observed in the treated eye. These findings may support the proposed biochemical mechanism for the therapeutic action of SLT. Clinical significance: The implication for clinicians is that SLT treatment in one eye may allow the fellow eye to benefit and provide a prediction on the fellow eye's response without subjecting both eyes to the rare but present complications of SLT.