The Great Commission is an important concept of missiological training and life wire of Christianity. This article is a critical review and reflection over the understanding and importance of this concept from the Old Testament background through the New Testament and its application to missiological training in the modern era. The article shows that the Great Commission is the singular theme that ran throughout the Scripture from the call of Abraham to the ascension of Jesus Christ and the mandate the Church is called to fulfil until the second coming of Christ. Missiological training, which is a mean to prepare labourers for missionary task of the Church, cannot be effective without a strong focus on the Great Commission mandate. Being the core of missionary task of the Church, the Great Commission should become the focus of all missiological training and dominant theme in the curriculum for the training of missionaries