Seventeen different media known to support the growth and isolation of members of the class Actinobacteria were evaluated as selective isolation media for the recovery of this microbial group from marine sediments samples collected in the Gulf of California and the Gulf of Mexico. A general selective isolation procedure was employed for six sediments and nearly 300 actinomycetes were recovered from the selective isolation plates. Full 16S rRNA gene sequencing revealed that the isolates belonged to several actinobacterial taxa, notably to the genera Actinomadura, Dietzia, Gordonia, Micromonospora, Nonomuraea, Rhodococcus, Saccharomonospora, Saccharopolyspora, Salinispora, Streptomyces, "Solwaraspora" and Verrucosispora. Previous works on marine sediments have been restricted to the isolation of members of the genera Micromonospora, Rhodococcus and Streptomyces. This study provides further evidence that Actinobacteria present in marine habitats are not restricted to the Micromonospora-Rhodococcus-Streptomyces grouping. Indeed, this first systematic study shows the extent of actinobacterial diversity that can be found in marine sediments collected in Mexico and probably, worldwide.