The aim of this study was to characterize multiexponential T2 (MET2) relaxation in a rat C6 glioblastoma tumor model. To do this, rats (n = 11) were inoculated with the C6 cells via stereotaxic injection into the brain. Ten days later, MET2 measurements were performed in vivo using a single-slice, multi-echo spin-echo sequence at 7.0 T. Tumor signal was biexponential in eight animals with a short-lived T2 component (T2 = 20.7 ± 5.4 ms across samples) representing 6.8 ± 6.2 % of the total signal and a long-lived T2 component (T2 = 76.4 ± 9.3 ms) representing the remaining signal fraction. In contrast, signal from contralateral grey matter was consistently monoexponential (T2 = 48.8 ± 2.3 ms). Additional ex vivo studies (n = 3) and Monte Carlo simulations showed that the in vivo results were not significantly corrupted by partial volume averaging or noise. The underlying physiological origin of the observed MET2 components is unknown; however, MET2 analysis may hold promise as a non-invasive tool for characterizing tumor microenvironment in vivo on a sub-voxel scale.