In summary, by employing HgTe QDs, the spectral sensitivity of QD/graphene phototransistors has been extended to midwavelength-IR spectral range up to 3 µm. The phototransistor shows no photosignal at room temperature, but at 80 K a specific detectivity of at least 6×10 Jones at a wavelength of 2.5 µm and a frequency of 67 Hz is obtained. The specific detectivity declines by 50 % at moderate light modulation frequencies of 700 Hz, well suitable for fast video recording. Higher specific detectivities may be achieved by increasing the QD layer coverage on graphene, optimization of the QD layer thickness, or utilizing different ligands and, by that, raising the operational temperature that optimizes the responsivity.