Background: Workplace social undermining antecedents can lead to serious consequences on nurses' performance and work related relationships that in turn affect the hospital overall quality and reputation. Aim: The aim of this study was to determine the effect of workplace social undermining on nurses' organizational trust and care cocreation. Subject and Methods: Design: Descriptive correlational design was applied to achieve present study aim. Setting: The study was conducted in El-Mehallah Cardiology Center Subject: all available (213) nurses. Tools: Three tools were used; nurses' perception of workplace social undermining, nurses' perception of organizational trust, and nurses' care co-creation questionnaire. Results: 55.4% perceived high levels of total workplace social undermining. 83.1% of nurses perceived low levels of total organizational trust and 63.4% of nurses had low levels of total care co-creation. Conclusion: there were significant negative correlations between workplace social undermining, organizational trust, and care co-creation. Recommendations: Hospital administration need to set a zero tolerance policy of workplace social undermining and continually asses its occurrence. Nurse supervisors need to recognize nurses' positive contributions, and share decisions, ideas, skills and knowledge with nurses.