In this paper, we consider the initial‐boundary value problem of semilinear damped wave equation utt−Δu + ut=|u|p with power
p=1+2n in an exterior domain. Blow‐up result in a finite time will be established in higher dimensions (n≥3), no matter how small the initial data are. A special test function will be constructed, and then, we obtain the blow‐up result by a contradiction argument. Copyright © 2016 John Wiley & Sons, Ltd.