This work was performed to relate the morphological features and all important properties of the natural rubber (NR) and bromobutyl rubber (BIIR) blends containing hybrid fillers. The BUR content was varied from 0 to 100 wt%. It is found that tensile and tear strength, hardness as well as resilience of blends tend to decrease with increasing BIIR loading. Regarding the blend morphology, phase inversion is observed when BIIR loading is >50 wt% where BIIR becomes a continuous phase. This result coincides with the marked improvement of thermal stability of the blends determined using thermogravimetric analysis and heat ageing method. Interestingly, that, the gas permeability of blends markedly reduces with an increase in BIIR loading up to 40 wt% when the relatively large elongated particles of BIIR dispersed phase is formed. The results indicate that the relatively large connected structure of the dispersed BIIR can act effectively as a gas barrier. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3985-3992, 2009