To evaluate the effects of a single bimatoprost implant administration on 24-hour intraocular pressure (IOP) lowering at 8 weeks, and 1-year IOP-lowering efficacy and safety outcomes. Multicenter, open-label, 12-month, phase 3b study (NCT04285580). Adults with open-angle glaucoma or ocular hypertension. Participants (n=31) received 10-μg bimatoprost implant in the study eye on day 1; IOP (sitting and/or supine) was measured with pneumatonometry every 2 hours throughout a 24-hour period at baseline and week 8. IOP was measured by Goldmann applanation tonometry (GAT) at hour 0 (8 am±1 hour) at baseline, weeks 8 and 16, and months 6, 9, and12. The primary endpoint was the week-8 hour-matched change from baseline in habitual position IOP over 24 hours assessed with pneumatonometry. Hour 0 IOP change from baseline measured with GAT in study eyes that received no additional (rescue) IOP-lowering treatment, treatment-emergent adverse events (TEAEs), and central corneal endothelial cell density (CECD) were evaluated through 12 months. The mean (standard deviation [SD]) baseline IOP at hour 0 was 24.2 (2.70) mmHg and 25.3 (7.15) mmHg by GAT and pneumatonometry, respectively. Pneumatonometer measurements of IOP taken over 24 hours at week 8 with the participant in habitual position (sitting from 8 am to 10 pm, supine from 12 am to 6 am) showed consistent IOP lowering through the day and night and reduced fluctuation in IOP. The range in IOP measurements over 24 hours was reduced from baseline by a mean (SD) of-1.6 (2.98) mmHg. All 31 bimatoprost implant-treated participants completed the 12-month study; 23 (74%) required no rescue IOP-lowering treatment. The mean (SD) IOP reduction from baseline at month 12 in nonrescued eyes was-4.3 (3.35) mmHg. The most common TEAE was conjunctival hyperemia (incidence 35.5%, 11/31). No implant-treated eye had a ≥ 15% loss in CECD from baseline. A single intracameral administration of the bimatoprost implant lowered IOP in the habitual position consistently throughout the day and night at week 8. The majority of participants continued to have reduced IOP for 1 year without additional therapy. The 1-year safety profile was favorable. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.