By using improved F-expansion method (IFEM), we study density-dependent space–time-fractional diffusion–reaction equation with quadratic nonlinearity (DDFDRE), which arises in mathematical biology. The fractional derivative is described in the sense of the CF derivative. Exact traveling wave solutions for DDFDRE are derived and expressed in terms of hyperbolic functions and rational functions. The IFEM is brief, efficient and easy to apply. It also can be used to solve many other fractional nonlinear evolution equations.