Solid-state dye-doped polymers are attractive alternative to the conventional liquid dye solutions. In this paper, nonlinear properties of the dye Acid Fuchsin has been studied. The third-order nonlinear optical properties of Acid Fuchsin dye in 1-butanol and dye-doped polymer film were measured by the Z-scan technique using 532 nm diode pumped Nd:Yag laser. This material exhibits negative optical nonlinearity. The dye at 0.4 mM concentration exhibited nonlinear refractive coefficient (n2 = -8.72 × 10-8 and -10.308 × 10-8 (cm2/W) in liquid and solid media, respectively), nonlinear absorption coefficient (β = -7.69 × 10-4 and -8.294 × 10-4 cm/W in liquid and solid media, respectively) and susceptibility (χ(3) = 4.33 × 10-6 and 5.13 × 10-5 esu in liquid and solid media, respectively). These results show that Acid Fuchsin dye has potential applications in nonlinear optics. © 2007 Elsevier B.V. All rights reserved.