A palynological and carbon-isotope analysis was carried out from the mid-Cretaceous of the DSDP Hole 398D located in the southern flank of the Vigo Seamount (NW Iberian offshore). The Oceanic Anoxic Event 2 (OAE2) was presumably expressed in core 398D-56 (upper Cenomanian-lower Turonian). However, the lack of detailed isotopic studies, besides the barren or scarce key taxa from the previous biostratigraphical studies, did not allow to confirm the presence of this biological crisis yet. The δ13C analysis has been demonstrated to be a reliable method to locate this type of event elsewhere corresponding to a Carbon Isotope Excursion (CIE). A carbon-isotope analysis of the bulk organic matter in sediment samples showed a CIE between sections 3 and 2 of core 398D-56. Moreover, the palynological quantitative analysis consisted of at least 250 palynomorphs per sample, allowing us to differentiate four different palynological samples and to find out the response of the terrestrial and marine communities to the OAE2. The δ13C results from the organic bulk sediments of the studied samples are provided in this dataset. Samples were analyzed by Isotopic Ratio Mass Spectrometry (IRMS). In each analytical sequence, secondary standards used were IAEA-C-6 (−10.8‰ ±0.47), IAEA CH7 (−32.15 ‰ ±0.05) and IAEA C3 (−24.9 ‰ ±0.04). An average reproducibility for the bulk sample better than 0.3‰ (±1σ, n=3) was obtained. Carbon-isotope values were expressed in per mille (‰) deviation from VPDB (Vienna Pee Dee Belemnite) using the standard delta notation (δ13C).