The interaction between bovine serum albumin (BSA) and the anionic graft copolymers poly(sodium acrylateco-sodium 2-acrylamido-2-methyl-1-propanesulfonate)-graft-poly(N,N-dimethylacrylam ide) (PNaA-co-NaAMPS)-g-PDMAMx) was investigated within the acid pH region, 2 <= pH <= 7. The weight percentage, x, of the poly(N,N-dimethylacrylamide) (PDMAM) side chains varied from 0 up to 75% (w:w). When BSA and P(NaA-co-NaAMPS)-g-PDMAMx are oppositely charged, i.e., when pH is lower than the isoelectric point of BSA, the two macromolecules associate through Coulombic attractions. When the anionic graft copolymer is rich enough to the nonionic PDMAM side chains, x >= 50% w:w, the associative phase separation is practically prevented, as revealed by the turbidimetric study of the BSA/P(NaA-co-NaAMPS)-g-PDMAMx mixtures in aqueous solution vs pH. In addition, the viscosity measurements support the formation through a charge neutralization process of a rather compact protein-polyelectrolyte complex stabilized by the hydrophilic PDMAM side chains grafted onto the anionic copolymer backbone.