We report in this paper photoinduced-dewetting phenomena observed for thin films (thickness < 100 nm) of a series of dendritic liquid crystalline materials with different spacer length (carbon number changing from n = 6 to 12) at their azobenzene units in the periphery. Spincast films of these dendrimers were prepared and exposed to UV light (365 nm) at various photon doses at room temperature. Atomic force microscopic observations of the dewetting forming process were performed step by step with increasing the UV illumination time for the dendrimer with the shortest spacer (n = 6). We observed how the dewetting bumps appeared from an initially flat spincast film and finally reached ca. eightfold of the initial film thickness. The dendrimer with n = 8 exhibited dewetting but the mass migration distance was significantly limited than that of n = 6. Dendrimers with longer spacer lengths (n = 10 and 12) did not exhibit dewetting behavior in the same conditions. These differences were discussed in terms of thermophysical properties of the materials.