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Geodetically‐derived deformation rates are sometimes used to infer seismic hazard, implicitly assuming that short‐term (annual‐decadal) deformation is representative of longer‐term deformation. This is despite geological observations indicating that deformation/slip rates are variable over a range of timescales. Using geodetic data from 2016 to 2021, we observe an up to 7‐fold increase in vertical deformation rate in mid‐2019 across the Pisia‐Skinos normal fault in Greece. We hypothesize that this deformation is aseismic as there is no temporally correlated increase in the earthquake activity (M > 1). We explore four possible physical mechanisms, and our preferred hypothesis is that the transient deformation is caused by centimeter‐scale slip in the upper 5 km of the Pisia fault zone. This is the first observation of shallow tectonic (i.e., not related to human activities) aseismic deformation on a normal fault globally. Our results suggest that continental normal faults can exhibit variable deformation over shorter timescales than previously observed, and thus care should be taken when utilizing geodetic rates to quantify seismic hazard. Plain Language Summary: Slip rates of active faults are used in seismic hazard assessment to infer the frequency of damaging earthquakes. However slip rates are known to be variable when measured using different methodologies (e.g., geodesy, geomorphology) and timescales (years to millennia) for many types of faults in a range of tectonic settings. Hence we need to observe slip rates for different time scales and try to understand the mechanism(s) that cause slip rates to vary. In this paper, we present observations of vertical deformation around an active normal fault in the Gulf of Corinth, Greece. We see that the deformation is non‐uniform during 2016–2021 (the time period of data availability), and we analyze the data to find that the deformation rate increased in mid‐2019. To try and understand the physical mechanism that may have caused this increase in deformation rate, we use simple modeling to test four different hypotheses. We find that the best fit to the observations is for centimeters of slip occurring on shallowest few kilometers of the fault. Our results highlight the importance of understanding short‐term (annual‐decadal) processes happening on active faults, and the potential pitfalls of using slip rates measured over short‐timescales to infer seismic hazard. Key Points: Spatial variations in vertical ground motion (uplift/subsidence) correlate with the mapped trace of the Pisia‐Skinos fault in GreeceThe ground deformation is non‐uniform over the 6 years studied, and shows an up to 7× increase in rate, lasting at least 3 yearsThis transient interseismic deformation is hypothesized to be caused by shallow aseismic centimeter‐scale slip on the Pisia‐Skinos fault [ABSTRACT FROM AUTHOR]