This study examines the conditions and effects of partially performed obligations in domestic law and two international instruments (the 1980 CISG and the UNIDROIT Principles). An obligation may remain only partially fulfilled or circumstances may prevent continued performance. If partial performance is not accepted, the obligor must still fulfill the entire obligation. However, where partial performance can be accepted, the conditions under which it discharges the obligor’s responsibility must be clarified. This inquiry considers whether the obligation is divisible, the parties’ intentions, and the roles of both obligor and obligee. It also explores the consequences of incomplete performance in matters such as transfer of property, payment of money, or performing or refraining from specific acts. Employing a library-based and comparative method, the research analyzes the relevant provisions of the CISG and the UNIDROIT Principles. Findings indicate that acceptance or rejection of partial performance depends on the nature of the obligation, the parties’ agreement, and the circumstances of the contract. In some instances, partial performance may be accepted as satisfying a segment of the obligation, thereby releasing the obligor to that extent. This study seeks to clarify these conditions and offer practical solutions for judicial practice. As a fundamental comparative investigation using library-documentary sources, it aims to elucidate the legal status of “partially performed obligations” in domestic law alongside the two aforementioned international instruments.