This chapter discusses the methods of studying behavioral lateralization in invertebrate animals. A number of studies have provided evidence of lateralized behavior and cognitive functions in a range of invertebrate species of different phyla such as Arthropoda (Insecta, Arachida, and Malacostraca), Mollusca (Gastropoda and Cephalopoda), and Nematoda. Here we report the findings of research conducted on lateralization in invertebrates with a specific focus on the methodology adopted. Behavioral asymmetries in the invertebrate line have been investigated by observing biases in different types of behavior that can be classified into six main groups corresponding to the six sections of the chapter. For each method, the advantages and disadvantages of using it are examined and the main findings on behavioral and brain asymmetries are reported and discussed.