The development of advanced cable materials are currently focused on the two interrelated problems: the improvement of the fire retardancy of halogen-free compounds and the extension of physical properties. These requirements are considerable particularly for the cable compounds, which have to comply with the requirements of LOCA qualifications (Loss of Coolant Accident) used in the nuclear power industry, or those compounds that are classified for LFHC cables (Low Fire Hazard Cables), used mainly in the civil engineering. Tightening of requirements in both fields continuously leads to search new and innovative solutions. One of them might be the using of Halloysite nanotubes (HNT) as an additive in these compounds. Therefore, this paper briefly describe the structural and mechanical influences of HNT in the different level of fulfilment (0, 1, 3, 7 wt%) in the LLDPE/HNT (linear low density polyethylene) nanocomposite compounds, which can be used as a primary cable insulation. Experimental samples were blended on the laboratory blades mixer Brabender W50 EHT and the plasticorder Brabender PLE 651 and then hot-pressed into thin sheets 0.25 mm thick. The influence of HNT on the base polymer matrix has been observed and evaluated through the average crystallite size and the average microstrain by automatic powder diffractometer Panalytical X'Pert PRO and through the imaging of scanning electron microscopy (SEM), which has been done by JEOL JSM-7600F. Despite the certain inter-phase tension between the base polymer and HNT, which has been observed by SEM, both measurements confirmed a relatively uniform dispersion of the HNT in the polymer matrix. According to the level of fulfilment, HNT has improved the mechanical behavior of the polymer nanocomposite significantly. Also, HNT affects the combustion process, which has been measured by Simultaneous Thermal Analyser SDT Q600. In particular, the end phase of combustion during the crust-formation has been most affected.