This dataset consists of coccolithophore abundances in the North Atlantic that were collected from 37 CTD casts during three RRS Discovery cruises (D350, D351, D354) in the spring and summer of 2010. Water samples (0.2-1 L) were collected from CTD casts and filtered through cellulose nitrate (0.8 µm) and polycarbonate (0.45 µm or 0.8 µm) filters, rinsed with trace ammonium solution, oven dried (30-40 °C, 6-12 h) and stored in Millipore PetriSlides. The filters were examined using a Leo 1450VP scanning electron microscope, with coccolithophores identified following Young et al. (2003), and enumerated from 225 fields of view (Daniels et al., 2012). The detection limit was estimated to be 0.2-1.1 cells mL-1. The samples were collected to investigate coccolithophore community dynamics in the North Atlantic as part of the Irminger Basin Iron Study (IBIS)(D350, D354), Extended Ellett Line (EEL)(D351) and a NERC Fellowship. Samples were collected on D350 by Martine Couapel, on D351 by Stuart Painter and on D354 by Alex Poulton and Mike Lucas. In the lab, samples were prepared and processed by Chris Daniels, Elena Maher and Jonathan Hurst, and were analysed for coccolithophore abundances by Chris Daniels and Jeremy Mirza. The data are held at the British Oceanographic Data Centre (BODC). Daniels, C. J., Tyrrell, T., Poulton, A. J., and Pettit, L.: The influence of lithogenic material on particulate inorganic carbon measurements of coccolithophores in the Bay of Biscay, Limnol. Oceanogr., 57, 145-153, doi:10.4319/lo.2012.57.1.0145, 2012. Young, J. R., Geisen, M., Cros, L., Kleijne, A., Sprengel, C., Probert, I., and Ostergaard, J.: A guide to extant coccolithophore taxonomy, J. Nannoplankt. Res. Special Issue, 1, 1-132, 2003.