Lightweight structural composites are finding applications in aerospace structures, deep sea pipe insulation and electronic packaging. In most of these applications, coefficient of thermal expansion (CTE) gains attention for either increased dimensional stability during service conditions or reducing thermal stresses at interfaces. Development of new composites with controlled CTE is highly desired. In the present study, hollow micro-particle (microballoon) filled vinyl ester matrix composites, referred to as syntactic foams, are evaluated for CTE. To analyze the effect of wall thickness and volume fraction of microballoons, study was conducted on six different types of syntactic foams containing three different microballoon densities, namely 220, 320 and 460 kg/m3, in two different volume fractions (?=0.3 and 0.6). The addition of glass microballoons enhanced dimensional stability of the composite by resulting in a reduction of the CTE by up to 60.4% in comparison to the neat vinyl ester resin. The experimental results revealed decrease in the CTE values with increase in ?. The effect of ? on the CTE of syntactic foams was stronger than that of the microballoon wall thickness. Theoretical predictions of CTE were obtained by using Turner's model which was modified by accounting the effect of microballoon wall thickness. The theoretical results closely matched with experimental results showing a maximum difference of ±15%. The results of this study can be helpful in designing composites for applications requiring precise control over their thermal expansion properties.