Aim: Whether pupillary expansion during phacoemulsification causes a change in postoperative intraocular pressure (IOP) is currently unknown. However, a growing proportion of patients can present with concurrent glaucoma and cataracts, which poses an increased risk of having small pupils and makes finding the answer to this question imperative for treating physicians. Materials and methods: This was a retrospective, observational cohort study which utilized data from 2008 to 2016 from the University Hospital, Newark, New Jersey, USA. All patients with primary open-angle glaucoma (POAG) who underwent phacoemulsification with pupillary expansion were considered for inclusion. Cases were subsequently excluded if they had prior incisional glaucoma surgery, if phacoemulsification was combined with another surgery, or if they had any incisional surgery in the eye 1 year preoperatively or postoperatively. The control group was made up of patients without POAG. The primary outcome was IOP. Results: Thirty-seven eyes from 31 glaucoma patients and 29 eyes from 28 control patients met inclusion criteria. The mean IOP in the POAG group increased from 15.0 ± 4.6 mm Hg to 15.9 ± 3.5 mm Hg after 1 year, whereas the control group decreased from 14.1 ± 3.6 mm Hg to 11.9 ± 3.9 mm Hg. Multivariate analysis showed that glaucoma was associated with a 5.56 mm Hg increase in IOP at 12 months postoperatively. The average number of glaucoma medications decreased significantly from 1.7 ± 1.4 at the baseline to 1.3 ± 1.3 after 1 year. Conclusion: In contrast with non-POAG patients, no significant drop in the mean IOP was noted after complex cataract surgery for this cohort of glaucoma patients, although medication burden significantly decreased and VA improved significantly. Clinical significance: Phacoemulsification with intraoperative pupillary expansion in POAG patients may not decrease IOP after 12 months but it can decrease the number of anti-glaucoma medications they take.