As a part of a screening program for natural products from microorganisms, 465 actinomycetes strains and 278 fungal strains were isolated from 44 seaweed specimens (Rhodophyta and Phaeophyta), collected in the Iberian peninsula seashore (Atlantic and Mediterranean coasts). Six different isolation procedures were followed, and seven isolation media were used, some of which included seawater in their composition. The isolated microorganisms were identified to the level of species or genus by microscopic morphology. Determination of species of Streptomyces was performed through total fatty acid analysis by gas chromatography. Richness and diversity of the Streptomyces and actinoplanetes species isolated from the seaweeds are compared, taking into account the geographic location of the samples. Most of the fungi recovered from these samples were terrestrial, although several marine species (Dendryphiella arenaria, Dendryphiella salina, Varicosporina ramulosa, Corollospora intermedia and Asteromyces cruciatus) were also isolated.