A fraction of the volcanic plume that originated from the Eyjafjallajökull volcanic eruption on Iceland in 2010 reached the southern Iberian Peninsula in May 2010. The plume was monitored and characterized in terms of optical and microphysical properties with a combination of Raman lidar and star- and Sun-photometers. Our observations showed that the plume arriving at the Iberian Peninsula was mainly composed of sulphate and sulphuric-acid particles. To our knowledge, this is the first study of optical properties and inverted microphysical properties of volcanic sulphate particles in the lower troposphere/boundary layer based on multiwavelength Raman lidar measurements. A remarkable increase in the particle number concentration in the accumulation mode was determined from the inversion of the aerosol optical properties. The large Ångström exponents and low linear particle depolarization ratios (4–7%) indicated the presence of small and spherical particles. The particle effective radii ranged between 0.30 and 0.55 µm. In situ instrumentation confirmed an increase of sulphate particles at ground level during this period.