A systematic study of the photophysical properties and nonlinear absorptive optical limiting responses of the [60]fullerene dimer (C-60 dimer) and poly[60]fullerene (poly-C-60) polymer in room-temperature solutions is reported. The results are compared with those of C-60 and representative C-60 derivatives. While the absorption, fluorescence (spectrum, quantum yield, lifetime), and photoinduced electron-transfer properties of the C-60 dimer are somewhat different from those of C-60, they are qualitatively similar to those of other C-60 derivatives. The triplet-triplet absorption of the C-60 dimer is noticeably weaker than those of C-60 and other C-60 derivatives, corresponding to lower optical limiting responses of the C-60 dimer at 532 rm. However, the photophysical and nonlinear absorptive optical limiting properties of the poly-C-60 polymer are significantly different. The polymer solution shows much weaker fluorescence, barely detectable tripler-state absorption, and marginal optical limiting response. The different excited-state and nonlinear optical properties of the poly-C-60 polymer are explained in terms of new excited singlet-state decay pathways in the polymer that are not available in monomeric and dimeric C-60 molecules. In addition, the issue concerning significant excited-state fullerene cage-cage interactions in the C-60 dimer and poly-C-60 polymer is discussed.