Recently, theory and research have supported collective psychological capital (cPsyCap) as a core construct linked to positive outcomes at the group and team level. However, to date, little attention has been given to cPsyCap emergence, or development, through training interventions. To fill this gap, this mixed-methods study involved first validating an evidence-based Collective Psychological Capital Intervention(cPCI) within 20 teams (175 participants) comprised of law/non-law professionals and a wait-list control group of n = 175 used as a comparison. In addition, this research aimed to better understand how cPCI participant attitudes and beliefs changed, if at all, as related to care of self and others, and lastly, how the development of cPsyCap impacted how cPCI participants responded amid active volatile, uncertain, complex, and ambiguous (VUCA) contexts (active shooter, on-duty death of a colleague, off-duty suicide, and threat of job loss/furlough). The results of this research validated the efficacy of the evidence-based cPCI, confirming that cPsyCap can emerge or develop through intervention. In addition, rich qualitative data capstoned these findings by detailing the lived experiences of cPCI participants and teams and how their increases in cPsyCap positively changed their attitudes and behaviors towards self and other care, as well as their ability to respond amid active VUCA contexts. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]