Developing new biomaterials is an active research area owing to their applications in regenerative medicine, tissue engineering and drug delivery. Di-block copolymers, combining a hydrophobic block with a hydrophilic one, are good candidates to develop biomaterials, but they are often obtained with non-bio-derived components. To circumvent this issue, we used two biocompatible blocks: a hydrophobic block made of polyisoprene (PI) extracted from natural rubber, and a hydrophilic block consisting in recombinant elastin-like polypeptide (ELP). We report the synthesis and characterization of the polyisoprene-block-ELP copolymers, coupled via Michael addition between the double bond of the maleimide previously grafted onto the PI, and the thiol function of the C-terminal cysteine of the ELP. The resulting conjugate can self-assemble into well-defined nanoparticles of hydrodynamic radius of 35–45 nm in aqueous solution. These nanoparticles can encapsulate hydrophobic molecules, and therefore could be used as drug delivery systems for various hydrophobic drugs.