LDPE/PA-6 blends (75/25 wt/wt) were added with SEBS-g-MA (S) and/or an organoclay (20A) using different compounding sequences and the morphology and the properties of the blends or composites were investigated. An XRD study of the nanocomposites with pure polymers showed that 20A is intercalated by LDPE or PA-6 chains, whereas it is exfoliated by S if the clay concentration does not exceed 10 wt%. The SEM investigation showed that both S and 20A behave as efficient emulsifying agents for the LDPE/PA-6 blends. However, their effect on the mechanical properties was found to be opposite: S enhanced toughness but lowered the stiffness, whereas 20A improved the elastic modulus but impaired the impact properties. When used together, these additives failed to have synergistic effects and the blends mechanical properties could not be improved strongly. A possible interpretation for this behavior was suggested, considering that the anhydride groups of S can competitively interact with the amine end groups of PA-6 and with the surface of the silicate layer of 20A. Nevertheless, an optimization of the compounding procedure and the use of appropriate proportions of S and 20A allow the preparation of composites with excellent morphology and a satisfactory balance of stiffness and toughness. POLYM. ENG. SCI., 49:1187-1197, 2009. (C) 2009 Society of Plastics Engineers