For the preparation of PEG 400 in paraffin oil non-aqueous biocompatible emulsions, the stabilization efficiency was compared for two well-defined poly(butadiene)-block-poly(2-vinylpyridine) (PBut-block-P2VP) block copolymers, with similar molecular weights but different compositions. The PBut128-block-P2VP50 and PBut189-block-P2VP37 samples, designated as copolymer A and B, respectively, are self-organized in paraffin oil as micelles with a P2VP core and a PBut corona. The PEG 400/paraffin oil emulsion characteristics were determined as a function of the copolymers concentrations and phase ratios. Higher static and shear stabilities were obtained for emulsions stabilized by copolymer B than for those obtained in the presence of copolymer A. A further difference concerns the droplet size, relative viscosity, and loss modulus values obtained at a given dispersed phase volume fraction. At constant copolymer concentrations, it appeared that copolymer B, with a longer PBut sequence, is a more efficient emulsifier and stabilizer than copolymer A. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41390.