This paper presents the technique for the critical infrastructure (CI) risk assessment based on Failure Modes, Effects and Criticality Analysis (FMECA), modified for multiple failures’ criticality assessment. The multiple failures (MFs) are significant contributors to risk in critical infrastructure. In spite of the low frequency of multiple failures’ occurrence, the severity of their consequences could lead directly to the CI’s accident and malfunctions. The influences of multiple failures should be taken into consideration as early as possible at the design stage. The paper presents classification of MFs, their root causes and coupling factors that stipulate the common susceptibility of systems to shared cause. The common cause failures (CCFs) are a subset of the dependant multiple failures. The qualitative procedure developed in the paper considers the consequences’ severity of CCFs on different I&C system levels. The total severity of CCFs is presented as a sum of severities for each level. The results of FMECA for single independent failures are taken as initial data to perform FMECA for MFs