Inter-governmental relations have been around the world ever since countries like the United States moved from a confederation system to a federal structure. Although the degree of interaction varied, there was inter-governmental interaction during the unitary structure. Eventually, through coming together or holding together, states were adopting federalism there by formal IGR. Ethiopia rushes into extreme sense of ethnic federalism beginning with small models as a reference to be applied among the then structure of effective political federations. Witnessing this false start, the 1991 federalism of Ethiopia was showing bad signals which indicate both systems based and implementation oriented problems. Meanwhile at the mid of 2018 there comes “national change” after three decades. The change constitutes preparation of a new IGR proclamation, assigning of MOP as collaborator of HOF in IGR issues replacing MOFA, conciliatory program to disputes of parties and regions, and promises for free and fair elections as well as the expansion of the political landscape and economic transformation. Following this, there were dynamics in Intergovernmental relations of horizontal of constituent units in Ethiopia. Especially the change has some visible dynamics on Amhara and Oromia horizontal IGR. This study investigated the current dynamics and implications of Intergovernmental relations of Amhara and Oromia regional states of Ethiopia since 2018 using constructive paradigm through case study design of a research. The researcher found that as a dynamics there was a new proclamation which supposed to strength their relationship, however not impllemented yet except a discussion just to begin its application. Concerning their over all IGR after mid 2018 the researcher from its sources confirmed that there are deterioratig symptoms of horizontal interaction in each regional state more than before the transition. Hence, the post mid 2018 IGR like some failed national security issues, it eventually get worse than the pre transition Amhara and Oromia interactions.