Summary: It has been shown that stable aqueous dispersions of nanoparticles of the rigid‐rod ladder‐type polymer poly(benzo‐bisimidazobenzo‐phenanthroline) (BBL) can be prepared in order to facilitate BBL processing. The obtained dispersions have a controllable particle size in the range between 50 and 150 nm and, consequently, the deposition of layers by spin‐coating or drop‐casting is realized. The resultant films exhibit a particulate structure and their morphology has been characterized by means of SEM and AFM. Upon investigation of the BBL dispersions in organic field‐effect transistors an ambipolar charge carrier transport has been observed, which presumably is related to the presence of mobile ions.