The outburst of the COVID-19 pandemic challenged vulnerable populations such as individuals with significant mental illness. In this fresh focus, we describe the innovative development of the UPSIDES mental health peer support intervention, in face of the COVID-19 pandemic in Israel. While the research program is still ongoing, in this paper we focus on the processes and lessons learned from dealing with the rapidly changing circumstances of the pandemic. We portray additional activities conducted above and beyond the UPSIDES protocol in order to maintain continuation and prevent dropout. We learned that an essential combination of keeping a close adherence with the core peer principles and UPSIDES' systematic program and the use of flexible telecommunication means, helped to maintain social connection and service users' participation throughout these times. The sudden pandemic challenges appeared to level out power imbalances and accelerated the formation of reciprocal and supportive relational interactions within the intervention. These processes highlight experiential knowledge as a unique asset, and peer support services as useful in supporting individuals with significant mental illness throughout COVID-19.