This article reports on the self-assembly behavior of a negatively charged hyaluronan (HA) and an oppositely charged styrylpyridinium species (specifically SbQ) in aqueous solution. Turbidity and Zeta potential measurements were utilized to explore the formation of complex micelles. These nano-sized micellar aggregates have a core–shell structure composed of a hydrophobic inner core containing aggregated SbQ molecules and a hydrophilic HA shell layer. UV spectra and DLS experiments confirmed that the micelles are photo-crosslinkable. A dimerization reaction of the SbQ molecules induced by UV light irradiation led to the crosslinking of the inner core, resulting in a decrease in the size of the micelles.