The Joint Declaration on the Doctrine of Justification which is considered to be ‘a milestone on the journey of ecumenism’ has a very significant place in the theological-ecumenical realm since it hoped to overcome the disunity between the protestant Churches and the Catholic Church at large. This work analyzes and redefines the JDDJ from a Pentecostal perspective, and proposes a new Pentecostal view of ecumenism for this century. The major questions that are considered here are: what is the ecumenical and ecclesiastical significance of this Joint Declaration in the 21st century, what are the neglected theological elements in the Joint Declaration, what are the controversial issues connected to the JDDJ and what challenge can it give to the present world of Christianity?. The JDDJ has become a basis for theological agreement and further discussions. This study also brings out ecumenical and theological understandings of the Pentecostal Church and substantiates the Pentecostal assessment of the JDDJ. The first chapter has two parts: the first part explains the research topic, methodology and the importance of the research; and the second part gives an outline of the Pentecostal movement and its theology mainly with regard to the doctrine of justification. The second chapter deals primarily with the significant stages and influences that helped for the formation of JDDJ. The last part of this chapter explains the responses of other churches to the JDDJ. The third chapter presents a Pentecostal response to the JDDJ, which starts with a positive evaluation and will be followed by a negative response to the same. The fourth chapter expounds the development of a paradigm model for the ecumenical thinking of the 21st century from a Pentecostal point of view. The Proposed slogan for this century can be “back to Pentecost” and be united in the love and power of the Holy Spirit. Because it is said that Pentecostal experience of the 1st-century Christianity has had a true Ecumenism, which was somehow lost in the long run. Nevertheless, methodological shifts in the approach to ecumenism can still make a change. When such a step is taken, the good news of unity of Christians will become a reality. Only then one can say that the condemnation of the 16th century regarding the doctrine of justification is invalid.