We have previously demonstrated that solution-cast films of conjugated polymers with grafted alkyl side chains comprise clearly identifiable domains ca. 10 nm in size upon solvent evaporation. Here we show that these nanodomains indeed serve as basic units for morphological development in poly(9,9-di-n-octyl-2,7-fluorene) (PFO) films during cold crystallization. Results of our microscopic and diffraction observations indicate that the cold crystallization process involves intradomain nucleation and growth, followed by nanodomain alignment and coalescence into fibrils in the sub-micrometer length scale via thermally activated adjustment of nanodomain orientation. An analogy with oriented aggregation (or oriented attachment-coalescence) behavior of nanocrystals of metal oxides is drawn; the relevance to recently proposed models of polymer crystallization via primary nucleation induced at the growth front is addressed.