Widespread observations of tremor and slow slip in different tectonic environments (Rubinstein et al. , 2009; Schwartz and Rokosky, 2007) reveal that these newly recognized processes play fundamental roles in accommodating and marking fault motion. Understanding the relationship between fault dynamics, stable (slow) slip, and more rapid earthquake rupture, however, requires a reliable method of identifying and characterizing slow‐slip phenomena. These tasks are particularly challenging in offshore environments where the investigation of plate boundary processes, especially within subduction‐zone megathrusts, typically relies, at least in part, on ocean bottom seismometers (OBSs). OBS deployments are increasingly common and have improved our ability to detect offshore earthquake swarms (e.g., McGuire et al. , 2012), but their utility for detecting or locating seismic tremor associated with slow slip has not been investigated in detail. Here we demonstrate that seismic tremor associated with the deep extension of the Alpine fault has been recorded on an OBS network lying off the west coast of New Zealand’s South Island (Stachnik et al. , 2012; Yang et al. , 2012). We focus on time windows known to contain tremor based on land observations (Wech et al. , 2012) and identify coherent tremor signals on OBS stations at distances of as much as 150 km. Applying routine tremor processing techniques (Wech and Creager, 2008), the envelopes of the OBS signals were correlated against each other and with land stations to constrain tremor epicenters. This correlation highlights the performance of OBS stations in the tremor frequency band (∼1–10 Hz), underscoring the potential effectiveness of OBS networks in constraining slow‐slip processes offshore. With the increased emphasis on OBS data collection in ongoing and future experiments, …