Immunofluorescence is an important immunochemical technique that utilizes fluorescence-labeled antibodies to detect specific target antigens. It is used widely in both scientific research and clinical laboratories. Immunofluorescence allows for excellent sensitivity and amplification of signal in comparison to immunohistochemistry. However, analysis of samples labeled with fluorescence-labeled antibodies has to be performed using a fluorescence microscope or other type of fluorescence imaging. There are two methods available: direct (primary) and indirect (secondary) immunofluorescence. Here, we describe the principle of immunofluorescence methods as well as the preparation of fresh-frozen and formalin-fixed, paraffin embedded tissues for both direct and indirect immunofluorescence labeling.