In this paper, we discuss a newly characterized compound, ZrW2O8, that has been introduced into the composite materials with an adjustable and low thermal expansion for electronic applications. Offering a negative coefficient of thermal expansion (CTE) of approximate -9×10-6/°C in a large temperature range, ZrW2O8 was used as a particle filler in polymer-matrix composites. The paper presents two kinds of composites, that is, polyester and epoxy with various volume fractions of ZrW2O8. The CTEs of the polyester/ZrW2O8 and epoxy/ZrW2O8 composites have been proven adjustable in the ranges of 94 to 56×10-6/°C and 54 to 18×10-6/°C, respectively, with ZrW2O8 filler from 0 to 30 vol%. In addition, the analysis about the interfaces between the matrices and filler indicated that the interfaces may be beneficial to reduce the overall thermal expansion of the composites. The methods to further decrease composite CTEs are also discussed.