Over the past three decades, we have dramatically increased our knowledge on the types of bacteria playing key roles in the degradation of oil hydrocarbons in the ocean. However, there remains a lack of complete understanding regarding the full diversity of species contributing a role in hydrocarbon degradative processes. Recent evidence highlights the cell surface, or ‘phycosphere’, of micro-algae as a new and largely underexplored biotope in the ocean that harbours novel taxa of hydrocarbon-degrading bacteria, including obligate hydrocarbonoclastic bacteria (OHCB). OHCB are a ‘specialised’ group exhibiting an almost exclusive requirement for hydrocarbon substrates as a sole source of carbon and energy. Several novel species of OHCB, including one new family, were recently discovered from laboratory cultures of marine micro-algae and more likely await discovery. The protocol below provides a detailed description for isolating these types of organisms from marine micro-algae based on their ability to degrade volatile low-molecular-weight hydrocarbons, aliphatic hydrocarbons, and/or polycyclic aromatic hydrocarbons.