PURPOSE: While Wendell Hughes popularized the tarsoconjunctival flap for lower eyelid reconstruction, most modern procedures are derived from the technique described by Köllner in 1911. This study reviews the history, techniques, and outcomes of a large series of patients treated with a modified Köllner flap. METHODS: In this observational cohort study, medical records and photographs were reviewed in patients undergoing surgery between 2005 and 2020. Patient demographics, complications, secondary interventions, and outcomes were evaluated. RESULTS: Marginal defect size ranged from 12 to 41 mm among the 140 study patients. Ancillary procedures included lower eyelid conjunctival flaps (n = 64) and septal orbicularis flaps (n = 68). The anterior lamella was reconstructed with skin grafts (n = 86), flaps (n = 10), or combined flaps/grafts (n = 44). Pedicle division was performed 23 to 84 days after primary repair. Subsequent interventions included steroid injection (n = 10), cryotherapy (n = 10), marginal erythema treatment (n = 9), and upper eyelid retraction repair (n = 6). Tearing (6.5%) and dryness (10%) were the most common postoperative symptoms, with most patients (78.6%) being asymptomatic. A good-excellent functional outcome was achieved in 94.3% and cosmetic outcome in 85.0% of cases. Defects <30 mm in width (P = 0.0001), defects not involving a canthus (P = 0.0158), and upper eyelid skin graft donor sites (P = 0.0001) were associated with better outcomes. CONCLUSIONS: The Köllner tarsoconjunctival flap is an effective technique to repair moderate-large lower eyelid defects, with the majority of patients achieving good-excellent cosmetic and functional outcomes. Factors associated with a poorer result include marginal eyelid defects ≥30 mm in width, defects involving a canthus, and non-upper eyelid skin graft donor sites. Most patients are asymptomatic after surgery.