The natural magnesium silicate, sepiolite (trade name Pansil), can partially substitute (up to 30%) for carbon black without important losses in physical properties and occasionally can improve them. In the NR-based compounds, as the substitution takes place, vulcanization times and Mooney viscosities decrease. Tear and abrasion resistances are lower. The same effects are observed in the SBR-based compounds, though in this case, the addition of a silane coupling agent (Silane A-189) counteracts the negative effects of the sepiolite, and the obtained values are clearly better than those with only carbon black. According to tan δ behavior in truck tire tread compounds, this filler type gives a higher wet grip resistance, but rolling resistance would be adversely affected by its use, though the presence of a silane coupling agent diminishes these effects. On the contrary, in passenger tire tread compounds, the partial substitution for carbon black seems to increase the wet resistance too, without a pronounced damage in rolling resistance. In this case, the addition of the silane coupling agent produces an increase in wet skid resistance and a decrease in rolling resistance. Based on laboratory tests, rolling resistance increases in all cases, mainly when the sepiolite was modified with silane. Wet skid resistance showed no variations. Clearly, it would be desirable to confirm our observations by an actual tire test.