Abstract. This article explores Iran-Ottoman relations during the Qajar era (1794–1925), highlighting both cooperation and competition between the two neighbors. Their collaboration brought significant achievements in economy, culture, politics, and security, while conflicts—mainly rooted in border issues, ethnic minorities, and foreign interventions (particularly Russian and British)—often led to wars. Despite these tensions, efforts to maintain peaceful relations marked this era as relatively stable compared to earlier periods like the Safavid, Afsharid, and Zand dynasties. Key events such as the First and Second Treaties of Erzurum reflect the deepening of bilateral ties. Although full success was not achieved, this period holds a notable place in the history of both nations for fostering cooperation in political, cultural, economic, and military spheres. The study adopts a descriptive and library-based research approach, concluding that these shared interests are strong foundations for continued collaboration.