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Optical absorption spectroscopy was performed on thin films of the perylene imide dye PDI8-CN2 during film growth by physical vapor deposition. The spectra showed an energy shift of 40 meV for the lowest energy transition with increasing film thickness from a sub-monolayer thickness regime to about 40 nm average film thickness with a clear step indicating the complete formation of the first monolayer. To analyze the observed characteristics a model was developed which is based on different contributions of transition dipole coupling in different crystalline directions. Clear dominance of intralayer coupling in the a–b crystal plane was found whereas interlayer coupling was found to be negligible. This was rationalized by the presence of alkyl chains as a spacer between the aromatic cores oriented along the c-direction. Atomic force microscopy of the films revealed layer-by-layer growth for the first monolayers and confirmed a texture with the c-axis perpendicular to the surface. The growth mode was correlated with the extent of intermolecular coupling in the different crystalline directions. We will discuss perspectives to optimize electron transport in PDI8-CN2 thin films which have been proposed as molecular semiconductor in organic field effect transistors (OFET).