The growth of Mn films on W(110) substrates has been investigated at room temperature by means of in-situ scanning tunnelling microscopy (STM) and low-energy electron diffraction (LEED). Our results show that highly strained bcc δ-Mn can be stabilized on W(110) by pseudomorphic growth up to a local thickness of three atomic layers. Sequences of STM images measured at the same location of the sample reveal that islands of the first and second monolayer grow anisotropically along the [001] direction of the substrate. The nucleation of roughly rectangular islands with a local coverage of five monolayers starts when the total amount of deposited material exceeds 1.0 ML. Local coverages of four atomic layers do not occur. The onset of nucleation of fifth monolayer patches coincides with an increased Mn density, indicating the onset of strain relaxation. The growth of Mn/W(110) is compared to that of Fe on the same substrate. The evolution of the filling factor of different layers is fitted by a simple model.