This chapter addresses the probabilistic competing failure behavior, which extends the deterministic competing failure behavior addressed in Chapter 8 by considering uncertain or probabilistic failure isolation effects. As demonstrated by the case studies from the Internet of Things applications (WSNs, body sensor systems, and smart homes), the probabilistic competing failure behavior abounds in systems involving relayed wireless communications. Combinatorial methods are presented for reliability analysis of single‐phase systems with a single type of component LFs, multiple different types of component LFs, and random PT. Refer to  on a combinatorial procedure for analyzing reliability of single‐phase systems subject to multiple dependent PFD groups. Refer to  on addressing the probabilistic competing failure behavior in the reliability analysis of phased‐mission systems (PMSs).