Background <p>In cataract surgery, inadequate pupil dilation presents a major surgical challenge by narrowing the operation field and restricting visibility and movement. We aim to compare cataract surgery complication rates and clinical outcomes using different pupil expansion methods.</p> Methods <p>This retrospective cohort study grouped patients according to four techniques of mechanical pupil expansion techniques: sphincterotomy (<i>N</i> = 339), iris stretching (<i>N</i> = 242), iris hooks (<i>N</i> = 391) and expansion rings (<i>N</i> = 294). Incidences and odds ratios for major complications and outcomes were compared between the groups.</p> Results <p>This single-center study included 1266 adult patients who underwent routine cataract surgery with mechanical pupil dilatation. The mean (± SD) age was 75.5 (± 13.0) years and 727 (57%) patients were male. The risk of pseudophakic cystoid macular edema (PCME) did not differ between the groups. Iris hooks were associated with the highest incidence of posterior capsular rupture (PCR) (3.3%) as compared to sphincterotomy, stretching and expansion rings (0.9%, 0.4% and 1.4%, respectively, <i>P</i> = 0.016). However, this effect was not supported by multivariable analysis. Zonular dialysis tended to be higher among eyes operated with iris hooks and pupil expansion rings, compared with iris stretching and sphincterotomy (2.0% and 1.7%, respectively, <i>P</i> = 0.058) and was found to be independently associated with a specific mechanical pupil expansion method on multivariable analysis (<i>P</i> = 0.050). No differences were observed for other complications, intraocular pressure or best-corrected visual acuity (VA) gain. Surgeon seniority was a significant protective factor from postoperative uveitis on multivariable analysis (<i>P</i> = 0.032).</p> Conclusions <p>Our large cohort study found no difference between the groups regarding major complications or clinical outcomes, suggesting that all four methods may be equally safe.</p> Key messages <Emphasis Type="BoldItalic">What is known</Emphasis> <p>• In cataract surgery, inadequate pupil dilation presents a major surgical challenge by narrowing the operation field and restricting visibility and movement.</p> <p>• Different pupil dilation methods have been used, ranged from topical and intracameral mydriatics and visco-mydriasis to mechanical dilation maneuvers.</p> <p>• Four principal techniques of mechanical pupil expansion, including sphincterotomies, manual iris stretching, iris retracting hooks and pupil expansion rings, are available.</p> <Emphasis Type="BoldItalic">What is new</Emphasis> <p>• This single-center study included 1266 adult patients found no difference between the groups regarding major complications or clinical outcomes such as pseudophakic cystoid macular edema (PCME), posterior capsular rupture, zonular dialysis, intraocular pressure, uveitis or best-corrected visual acuity gain.</p> <p>• Surgeon seniority was a significant protective factor from postoperative uveitis.</p>