Cell-penetrating peptides (CPPs) are a class of short peptides that are known to translocate inside living cells through the cell membrane. Many CPPs show an ability to bind and deliver macromolecular cargoes such as DNA, RNA and protein into living cells, making them excellent transfection and transduction agents with low cytotoxicity. While their use is well established in mammalian cell systems, they have also been explored in the last decade as transfection agents in plant cells. Their efficacy has been demonstrated in both monocot and dicot clades as well as a variety of tissues and cell cultures, from leaves to protoplasts. Factors affecting CPP and CPP-cargo uptake have been addressed with specific attention to the plant cell wall and classes of CPPs utilized in plant cell systems. It has been shown that internalization of most free peptides in plant cells has been dominated by direct translocation across the cell membrane, while CPP-macromolecular cargo complexes and conjugates were translocated via macropinocytosis. Moreover, functionalization of CPPs resulted in generation of peptides with specialized cargo delivery attributes, e.g., for specific subcellular targeting. Thus, the use of CPPs in plants presents a promising method for plant transgenesis as well as genome regulation and modification.