Information about advances in immobilization techniques and biotechnology use of freshwater and marine microalgae is scattered. This work aims to bring together the main recent research about the topic. Passive and active immobilization techniques used on microalgae are listed and described in the text. Effect of immobilization on growth and metabolism of the cells is also reviewed. Current uses of immobilized microalgae include metabolite production, culture collection handling, obtaining of energy and removing of undesired or valuable substances from media (nutrients, metals and different pollutant agents). Applications of immobilized microalgae in environmental aquatic research have been recently increased: novel immobilization techniques as well as the use of living microalgae as biosensors in electronic devices designed to measure toxicity of substances and effluents demonstrated to be a very promising topic in biotechnology research. Recent research pointed out the advantages of mixed bacterial-algal co-immobilized systems in water treatment plants. Application of immobilized systems to the production of non-contaminant energy (as H(2) obtained from algal cultures) is also an important topic to be explored in the next years.