Fluorene-based polymer derivatives are promising materials for organic electronic devices because of their photoluminescence and electroluminescence, good film-forming ability, and favorable chemical and thermal properties. Although optical properties of polyfluorene have already been reported, most of the studies focused on the linear optical properties, whereas nonlinear optical characteristics have only recently received more detailed attention. Here, we report on two polyfluorene derivatives, poly(9,9 0 -n-dihexyl-2,7-fluorenediyl) (LaPPS 10) and poly(9,9 0 -n-dihexyl-2,7-fluorene-diyl-vinylene) (LaPPS 38), which present intense nonlinear absorption and fluorescence. Two-photon absorption cross-section properties of both polymers were characterized in the spectral range from 500 nm up to 900 nm, reaching peak values around 2000 G€ oppert Mayer units. Optical limiting behavior and twophoton-induced fluorescence of both polymers have also been investigated. Furthermore, the first molecular hyperpolarizability of the polymers was also studied using hyper-Rayleigh scattering. In addition, the three-photon absorption (3PA) spectra of both materials were also investigated, and 3PA INTRODUCTIONIn the last decades, conjugated polymers have been explored as potential materials for electrical and optical applications. Within this class of materials, the combination of important features of polyfluorene derivatives, such as photoluminescence and electroluminescence, 1,2 thermal and oxidative stability, good film-forming, and hole-transporting properties, 3,4 still offer room for further investigation, notably concerning their optical behavior. Although the linear optical properties of polyfluorene derivatives have been the subject of a large number of investigations, the nonlinear optical characteristics, including two-photon absorption (2PA), has only recently received a deeper attention.