Effects of filler and rubber polarity on the distribution of filler in butadiene/nitrile rubber (BR/NBR) blends were investigated, using the dynamic mechanical thermal analysis technique. As 30-phr filler is added, the reduction in heights of damping peaks (tan delta (max)), attributed to the dilution effect, was observed. It was also found that the BR phase in the blends, compared to the NBR phase, is more preferential for small- and large-particle size carbon blacks to reside, probably because of the lower viscosity and lower polarity of the BR phase. The addition of silica instead of carbon black leads to an increase in filler migration to the NBR in the 20/80 BR/NBR blend, which is attributed to the strong silica-NBR interaction. In addition, an increase in NBR polarity promotes carbon black migration to the BR phase.