Arginine-rich cell-penetrating peptides (CPP) are widely employed as delivery vehicles for a large variety of macromolecular cargos. As a mechanism-of-action for induction of uptake cross-linking of heparan sulfates and interaction with lipid head groups have been proposed. Here, we employed a multivalent display of the CPP nona-arginine (R9) on a linear dextran scaffold to assess the impact of heparan sulfate and lipid interactions on uptake and membrane perturbation. Increased avidity through multivalency should potentiate molecular phenomena that may only play a minor role if only individual peptides are used. To this point, the impact of multivalency has only been explored for dendrimers, CPP-decorated proteins and nanoparticles. We reasoned that multivalency on a linear scaffold would more faithfully mimic the arrangement of peptides at the membrane at high local peptide concentrations. On average, five R9 were coupled to a linear dextran backbone. The conjugate displayed a direct cytoplasmic uptake similar to free R9 at concentrations higher than 10 μM. However, this uptake was accompanied by an increased membrane disturbance and cellular toxicity that was independent of the presence of heparan sulfates. In contrast, for erythrocytes, the multivalent conjugate induced aggregation, however, showed only limited membrane perturbation. Overall, the results demonstrate that multivalency of R9 on a linear scaffold strongly increases the capacity to interact with the plasma membrane. However, the induction of membrane perturbation is a function of the cellular response to peptide binding.