The design, synthesis, and properties of a novel, solution-processible organic semiconductor based on star-shaped oligothiophenes linked through flexible aliphatic branches to a carbosilane core are described. This four-arm dendrimer-like molecule not only forms smooth thin films on large surfaces but also shows improved monolayer formation compared to its linear prototype, α,α'-dihexylquaterthiophene (Hex-4T-Hex). For the new material, three different types of structural organization (nanowires and mono- and multilayers) were found, all of which are favorable for charge transport through the material in organic field-effect transistors. These processability and structural properties, in combination with high field-effect mobility, high current modulation, and a threshold voltage of ~0 V, suggest that star-shaped oligothiophenes with carbosilane cores are a promising new class of semiconducting materials for use in flexible organic electronics.