The main objective of this study is to measure and characterize the mechanical properties of the thermoplastic syntactic foams at the intermediate and high strain rates. The syntactic foam consists of the elastically deformable microballoons in the polypropylene matrix. The four types of syntactic foams and one polypropylene bulk specimen are prepared at same manufacturing process: 0, 20, 30, 40 and 50 volume percent of microballoons. Tensile tests are conducted at nominal strain rates ranging from 10-1 to 102 (1/sec). Elastic modulus, yield stress and rupture strain are measured and the effects of microballoons on the mechanical properties are studied. In addition, fracture surfaces are observed with ESEM (Environmental Scanning Electron Microscopy). Finally, the changes of fracture mode due to microballoons are discussed.