Novel luminescent electrospun (ES) fibers have been successfully prepared from a conjugated rod-coil block copolymer, poly[2,7-(9,9-dihexylfluorene)]-block-poly(methyl methacrylate) (PF-b-PMMA) using a single-capillary spinneret. Experiment results indicate that PF-b-PMMA ES fibers prepared from THF, THF/DMF (50/50), and DMF contain PF block aggregated structures of dot-like (5-10 nm), line-like (10-20 nm), and ellipse-like structure (25-50 nm), respectively. Such variation of aggregation size leads to a red-shift of the absorption or luminescence spectra. In addition, the fiber diameters decrease upon enhancing the DMF content. The present study demonstrates that blue light-emitting ES fibers are successfully prepared from conjugated rod-coil diblock copolymers and their aggregate morphology and photophysical properties could be tuned through use of selective solvent.