This paper discusses non-State actors’ motivation and capacity to develop and use chemical, biological, radiological or nuclear (CBRN) improvised weapons in attacks, as well as the possible consequences of such use. Six types of groups have been identified as potential CBRN weapons users that may increasingly be able to acquire relevant CBRN weapons-related knowledge, skills and possibly materials. As technical barriers still form a gap between the theoretical possibility and the operational reality, any potential future CBRN attacks would most likely be crude, low-level attacks, including chemical or radiological materials. CBRN attacks carried out by non-State actors in the future are likely to be more disruptive than destructive.