In this article we present polarization diversity in the wake-up path of a low-power wireless sensor node. Due to antenna diversity, the node shows an improved wake-up signal strength and optimized sensitivity in a multipath propagation environment. We verify the design using simulations and different measurement setups. The resulting combined antenna signal has a gain of +3 dB when both diversity antennas receive the same signal strength. In this case, the wake-up receiver has an improved sensitivity around −53.7 dBm. Furthermore, we introduce a smart antenna for the communication link by using just one extra antenna switch. The proposed design can be used for any wake-up receiver of this kind.