Background: Emotional dysregulation is considered a phenotypic finding that has a purported impact on older adults' peace of mind. Emotion regulation nursing intervention is a breakthrough treatment that has been empirically targeted to restore positive emotional states and strengthen mental clarity in the geriatric population. Aim: This study aimed to determine the effect of emotion regulation nursing intervention on emotional regulation difficulties and peace of mind among older adults. Design: A quasi-experimental methodological approach was applied. Setting: Two seniors' clubs that belonged to Egypt's Ministry of Social Solidarity, Alexandria Governorate were included.  Study participants: 80 older adults (aged 60 and above), randomly assigned into two equal groups. The study group received the study intervention, and the control group, received regular seniors' club services. Tools: 4 tools were used for data collection: 1) Mini-Mental State Examination Scale (MMES), 2) Brief version of the Difficulties in Emotion Regulation Scale: the DERS-16, 3) The Peace of Mind Scale: PoM, and 4) Socio-demographic and Health Profile of Older Adults Structured Interview Schedule. Results: The reported emotional regulation difficulties score was significantly reduced in the study group from 73.59±5.99 to 19.18±8.0 following the intervention (P<0.001) and was significantly higher than the control group's post-test percent score 70.63±4.20 (P<0.001). The peace of mind score increased from 11.70±7.84 to 24.91±0.56 among the study group following the interventions and was significantly higher than that of the control group's post-test percent scores 6.07±5.0 (P<0.001). Conclusion: Emotion regulation nursing intervention generated a significant reduction in older adults' emotional regulation difficulties and a significant improvement in their peace of mind. Recommendations: The present study finding provides support for the creation of a skill-based training program for all nurses who work with older adults in all settings about the importance of emotion regulation nursing intervention and how to implement them for older adults.