Scanning tunneling microscopy (STM) is employed to investigate the structural and morphological properties of Ni monolayers (ML) deposited on W(110) at room temperature. We observe almost perfect layer-by-layer growth for the first three atomic layers. At a coverage of about 6 ML, a transition to three-dimensional growth is found. The analysis of STM images in the submonolayer regime indicates that the coalescence of the islands triggers the formation of a 8x1 coincidence structure. In contrast to the preferential orientation expected from the twofold symmetric substrate, the islands in the first atomic layer have an irregular shape. Elongated Ni islands are observed in the second layer. The anisotropic island shape is ascribed to the anisotropic diffusion due to anisotropic strain in the underlying first layer. The edges of the Ni islands are oriented along the closed packed <110> directions of the growing Ni(111) film for Ni coverages above 5 ML.