The synthesis and comprehensive linear spectroscopic and nonlinear optical properties of a new BODIPY-based fluorene-containing derivative 4,4-difluoro-8-(4-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}phenyl)-1,3,5,7-tetramethyl-2,6-di[(9,9-di{2-[2-(2-methoxyethoxy)ethoxy]ethyl}-9H-fluoren-2-yl)ethynyl]-4-bora-3a,4a-diaza-s-indacene (1) are reported. The steady-state absorption, emission, and excitation anisotropy spectra along with fluorescence lifetimes of 1 were analyzed in organic solvents of different polarity. The degenerate two-photon absorption (2PA) spectrum of 1 was obtained over a broad spectral range by the open aperture Z-scan method using 1 kHz femtosecond excitation, and the 2PA cross section had a maximum value of ∼400 GM. The one-photon stimulated emission depletion spectrum of 1 was determined by a fluorescence quenching method with values of stimulated emission cross sections close to the corresponding ones of the ground state linear absorption. The nature of ultrafast relaxation processes in ...