Abstract Dislocations can be seen either as a linear domain of a crystal where atoms are misplaced, or through their long-range elastic strain fields. Transmission electron microscopy is sensitive to both aspects. Atomic-scale configurations within the dislocation cores can be imaged directly by high-resolution transmission electron microscopy and scanning transmission electron microscopy. On the other hand, the long-range lattice distortions induced in the crystal by dislocations give rise to a diffraction contrast in conventional transmission electron microscopy which can be used to image dislocation microstructures or to characterize their Burgers vectors. This chapter reviews the experimental techniques available in transmission electron microscopy to image and characterize dislocations.