Tissue engineering is defined as "an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function." The biological substitutes can be developed with the help of natural or synthetic materials. Polymeric materials are primarily used, because of the high variability in mechanical, physical, and chemical properties. Biodegradable polymers are object of the majority of studies, because of the ability to be degraded by the host organism, avoiding late stent thrombosis unlike permanent grafts. Poly-l-lactide acid (PLLA) is one of the most used polymers in research. In order to improve the material's bioactivity, in this work, PLLA surface was modified by grafted arginine-glycine-glutamine (RGD), a fibronectin derived adhesion motif, and serine-isoleucine-lysine-valine-alanine-valine (SIKVAV), a laminin derived motif, and rat cardiac (H9C2) and mouse (C2C12) myoblasts proliferation and differentiation on modified PLLA were evaluated. In order to verify the surface modification, x-ray photoelectron spectroscopy analysis was performed. After seeding, cells' viability was confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while proliferating cell nuclear antigen expression was used to investigate cell proliferation. Myf5, Myogenin and Myosin heavy chain were used to analyze cell differentiation. Moreover, RGD peptide slightly inhibited rat myoblast (H9C2) proliferation, whereas less strong effect was observed on C2C12. However, both cell lines showed to enhance the contractile phenotype in the presence of SIKVAV peptides. These results suggest that bioactive molecules grafting could be useful on polymeric scaffolds for guiding cell phenotype expression, and, to ultimately maintain adequate biological characteristics suitable for the tissue functional regeneration.