The centrepiece of Malaysia-Japan relations has consistently revolved around the Look East Policy (LEP) inaugurated in 1982 and further strengthened in 2013 as the LEP 2.0 under the Mahathir Mohamad and Najib Razak administration respectively. Although economic and social development under LEP and LEP 2.0 alongside security cooperation has significantly improved relations between both countries, political cooperation has been an often overlooked contributing factor. By employing the concept of party diplomacy, this qualitative case study contends that dominant party politics has exerted a substantial impact on the evolution of Malaysia-Japan relations by means of the direct or indirect interactions between the United Malays National Organisation (UMNO) and the Liberal Democratic Party (LDP). There are compelling evidences indicating that UMNO has engaged in political cooperation with the LDP, resulting in expedited negotiations in other areas of cooperation between the two countries. This paper builds upon the party diplomacy paradigm, which has received limited attention, particularly in its application to dominant parties as a case study. The study also aims to expand the existing literature on Malaysia-Japan relations beyond the limited scope of the LEP and LEP 2.0 by examining the relationship between both countries from the perspective of party diplomacy and dominant party politics.