We report on a method to achieve real-time dual-wavelength digital holographic microscopy with a single hologram acquisition. By recording both interferograms from two laser sources at different wavelengths in only one spatially-multiplexed digital hologram, we are able to independently propagate and apply numerical corrections on both wavefronts in order to obtain a beat-wavelength phase map of the specimen. This beat-wavelength being up to 10-100 times larger than the original wavelengths, we are in a situation where the 2? phase ambiguity of conventional DHM is removed and the phase measurement range of the technique is extended up to several tens of microns in height. The unique capability to perform such an operation with a single acquisition unables real-time dual-wavelength DHM measurements. Results on a moving micro-mirror are presented in this paper. We think that such a real-time dual-wavelength method represents a strong improvement to the current DHM state-of-the-art, and that it opens a whole new field of applications for this technique.