The performance of an energy detector operating over κ–μ shadowed fading is investigated. A novel closed-form expression for the average detection probability using the well-known probability density function-based method is derived. The unified framework, in terms of Fox's H-function, shows that the obtained results can be used for arbitrary values of fading parameters. On the basis of this derived analytical formula, the impact of key fading parameters on the performance of the energy detector is discussed. Furthermore, the accuracy of the analytical expressions is substantiated by Monte Carlo simulation results.