We demonstrate a novel approach to detection and localization of structural damages using Fiber Segment Interferometry (FSI). FSI is a long-gauge optical sensing technology for the measurement of elongation, characterized by nano-strain resolution and high sampling rate. This paper shows that low-amplitude transient strain changes caused by acoustic emissions can be measured with FSI and used to pinpoint the origin of events. This work examines results from tests conducted on the openLAB research bridge. During the experiment, several wires from the prestressing tendons were cut, creating damage along the central span of the bridge, and causing acoustic events. The 15 m central span of the bridge was instrumented with three FSI strain-sensing fibers, each 800 mm in length, bonded directly to the concrete surface in a linear arrangement along the girder. Each fiber contained five reflectors, forming four contiguous measurement segments. In FSI, the measurement corresponds to the change in elongation of the segment between adjacent reflectors. When a wire is severed, the event will propagate to each fiber and segment with a delay. A comparison of the differential delay can be used to triangulate the location of the damage. Of the 38 events nominally reported, 84% were successfully detected using FSI technology. Considering all measurement locations, we observed an average event amplitude of 717 ± 513 nε, well above the signal noise level of 34 ± 13 nε. Localization of the events was also successful, with an average absolute deviation from nominal damage location of 84 ± 43 mm and a maximum deviation of 175 mm. These results provide a strong indication of the potential of FSI for damage localization. Future development will extend this line of research to other sources of damage detectable with dynamic strain measurements.