Fish blood sampling requires specific techniques and skills that are fundamental for all kinds of analyses such as haematology, chemistry analysis, parasitology/bacteriology investigation, antibody titration, molecular diagnostic and many others. WorldFish and partners developed this quick guide on blood sampling from fish for: (1) blood serum isolation, (2) blood plasma isolation, (3) blood DNA extraction, (4) blood RNA extraction, or for (4) blood smear preparation on microscope slide.