PURPOSE: To evaluate the outcomes of phacoemulsification and intraocular lens (IOL) implantation in microphthalmos and nanophthalmos. SETTING: Moorfields Eye Hospital, London, United Kingdom. DESIGN: Retrospective case series. METHODS: Eyes with an axial length (AL) less than 21.0 mm had elective phacoemulsification and IOL implantation. RESULTS: One hundred three eyes (63 patients) were enrolled. The median AL was 20.65 mm (interquartile range [IQR], 20.26 to 20.86) and the median follow-up, 6.3 months. Complications occurred in 16 cases (15.5%). Zonular dehiscence, severe uveitis, and aqueous misdirection accounted for the majority of complications. Complication rates were 6 (7.3%) of 82 cases with an AL from 20.0 to 21.00 mm and 10 (47.6%) of 21 cases with an AL less than 20.0 mm (P=.0001). Only AL (odds ratio [OR], 0.52 per mm; P≤.0005) and abnormal intraocular pressure (IOP) of 22 mm Hg or more or on topical IOP control (OR, 10.1; P=.001) were significant independent risk factors for complications. For the cohort after adjusting for abnormal IOP, an AL less than 20.5 mm was associated with a 4 times higher odds of any complication (P=.028), an AL less than 20.0 mm was associated with a 15 times higher odds of any complication (P≤.0005), and an AL less than 19.00 mm was associated with a 21 times higher odds of any complication (P≤.0005). CONCLUSIONS: Phacoemulsification and IOL implantation in microphthalmos/nanophthalmos was challenging but appears safer than previously reported. A shorter AL and abnormal IOP were significant risk factors for complications.