The Council of Nicea in 325 AD became an important milestone in building the unity of the Christian faith. Although it took place before Christianity spread to Indonesia, its theological legacy continues to shape the collective identity of Christians and ecumenical dynamics in the midst of denominational diversity. The council produced the Nicene Creed, which not only formulated the doctrine of the Trinity more clearly, but also became the basis for efforts to unify faith in various Christian traditions. As a theological document agreed upon by various churches, the Nicene Creed became a symbol of shared faith that transcends denominational boundaries and cultural contexts, including in Indonesia. This article examines how an understanding of the Council of Nicaea influences the collective consciousness of Indonesian Christians, strengthening solidarity and reducing theological polarisation. Using qualitative research methods through a historical-theological approach and social psychology analysis, this study examines how the Nicene Creed plays a role in building ecumenical awareness in Indonesia. In this context, social psychology helps to understand how certain theological doctrines can shape group identity and encourage or hinder cross-denominational interaction. One of the challenges to ecumenism is the legacy of historical conflicts between denominations, often influenced by doctrinal differences and socio-political factors. Some research suggests that theological polarisation can be further amplified by external factors such as social media and identity politics. Social media contributes to shaping a more exclusive perception of religious identity, which can deepen the divide between groups. Meanwhile, there are studies that show that contemporary challenges such as the Covid-19 pandemic also impact the dynamics of ecumenism and show the challenges in building solidarity between theological schools. In the Indonesian context, awareness of the ecumenical values contained in the Nicene Creed can be an important instrument in reducing conflict and strengthening Christian brotherhood. A deeper understanding of the heritage of the Council of Nicea can help churches in Indonesia to develop a more inclusive mindset and respond to the challenges of theological polarisation. Thus, the legacy of the Council of Nicea not only plays a role in shaping the foundations of Christian theology, but also in supporting the broader ideals of ecumenism in Indonesia.