Virus Like Particles (VLPs) are self-assembling, nonreplicating, nonpathogenic, genomeless particles similar in size and conformation to intact infectious virions. The possibility of engineering VLPs to incorporate heterologous polypeptides/proteins renders VLPs attractive candidates for vaccine strategies, as well as for protein delivery for basic science. Among the wide number of VLP types, our expertise focused on both retro- and lentivirus based VLPs as protein delivery tools. In particular, here we describe a system relying on the finding that some HIV-1 Nef mutants are incorporated at high levels into both Human Immunodeficiency virus (HIV)-1 and Moloney Leukemia Virus (MLV)-based VLPs. Most importantly, these Nef mutants can efficiently act as anchoring proteins upon fusion with heterologous proteins up to 630 amino acids in length. This chapter describes the preparation of prototypic HIV-1 based VLPs incorporating Nef mutant-GFP fusion molecules. Besides having potential utility in the field of basic virology, these VLPs represent a useful reference model for recovering alternative retro- or lentiviral based VLPs for the cell delivery of polypeptides/proteins of interest.