Abstract—Deep earthquakes occur in subduction zones—they play a key role in the global tectonic model. There are only a few places on the Earth where deep-focus seismicity is observed on the continents in small localized areas at a considerable distance from the present-day subduction zones, in particular in the Vrancea region of the Carpathians. The strongest deep Vrancea earthquakes are felt at a distance of over 1000 km. They essentially define the seismic hazard for the East European platform, where either there are no local focal zones or these zones have small magnitudes. Therefore, studying deep Carpathian earthquakes is very important for adequate assessment of seismic hazard for the East European platform. We assume that although the strongest deep Carpathian earthquakes have been studied quite fully and thoroughly, not all existing information has been exhausted. The search for previously unknown primary sources may reveal new information about the macroseismic effect and, consequently, lead to more reliable and accurate earthquake parameter evaluations. This article examines the 1838 deep Carpathian earthquake using the original descriptions from primary sources. The earthquake magnitude has been determined by means of a new approach based on minimizing the discrepancies between the calculated and observed shaking intensities at all localities. It is shown that the magnitude of the 1838 earthquake is underestimated in the published catalogs by about 0.5 unit. We believe that the main reason is that the previously used macroseismic data in the far-field zone are not sufficiently complete.