A new poly(fluorene-co-carbazole) (PFC-1) with a large substituent group (ADN, a naphthalene-anthracene derivative moiety) at the 9-position of carbazole was synthesized. Compared with poly(fluorene-co-carbazole)s that have an alkyl substituent group at the 9-position of the carbazole, the UV-vis absorption (or photoluminescent emission) peaks of PFC-1 are in almost the same position both in solution and in the solid state, whereas films of the former give peaks at longer wavelengths than those in solution. The photoluminescent (PL) spectra of PFC-1 indicate that the attachment of ADN to the poly(fluorene-co-carbazole)s gives rise to an efficient blue emission from non-aggregated ADN. There is no difference evident between PFC-1 and other reported poly(fluorene-co-carbazole)s in PL quantum yield, thermostability, and electrochemical behavior, which suggests that PFC-1 is an efficient blue emitter.