Practitioners and researchers alike recognize the positive influence insiders' behavior can have on information systems (IS) security. This awareness has resulted in a research stream focused on the performance of protective behaviors. We contribute to this research stream by extending an oft-cited theory in the information security literature—protection motivation theory (PMT)—to include the relationship of insiders' psychological capital (PsyCap) with the mechanisms of PMT. PsyCap is a construct of role-breadth psychological capacities and resources embodying important work-related motivational resources. Therefore, given the varied facets central to PMT, determining the relationship of PsyCap with each distinct PMT mechanism is an important contribution. Furthermore, prior research has established that individuals can develop their PsyCap. Consequently, considering the relationship of role-breadth PsyCap with the PMT mechanisms provides an important and malleable, motivational antecedent that complements PMT and is absent from most assessments of the contemporary PMT model. We find support for PsyCap's relationship with the mechanisms of PMT and suggest opportunities to develop PsyCap in conjunction with other organizational security efforts. We present our findings, discuss their implications for research and practice, and highlight several opportunities for future research. •Extended PMT model is proposed that includes the relationship of insiders' PsyCap.•PsyCap uniquely relates to each threat and coping appraisal mechanism of PMT.•Via the facets of PMT, PsyCap indirectly relates to protection motivation and PMBs.•Higher levels of PsyCap are related to more PMBs and higher protection motivation.•Opportunities exist to build insiders' PsyCap and improve information security.