In an increasingly fierce knowledge-based competitive era, one of the most urgent challenges facing Korean firms is securing source technologies. To obtain these increasingly important source technologies, firms have not only engaged in internal R&D efforts but have also actively formed alliances with foreign firms to acquire the necessary source technologies. In particular, since relying solely on internal technology development has inherent limitations for rapidly developing source technologies in a rapidly changing business environment, designing knowledge alliances with advanced foreign firms has become increasingly important for the domestic acquisition of source technologies. However, simply entering into a strategic alliance with an external firm does not automatically ensure the acquisition of source technologies. This is because source technologies are mostly tacit in nature—embodied in people—and the formation of close relationships between partners is a prerequisite for technology transfer. Despite this importance, existing studies have insufficiently analyzed methods for successfully introducing tacit technology transfer from the perspective of alliance partner relationship characteristics. Against this research background, this study examined, using foreign joint ventures in Korea as the sample, how joint venture performance can be enhanced through tacit technology transfer from the perspective of partner relationship dimensions. Specifically, the study empirically examined how the interaction effects between the tacit characteristics of technology transferred from joint venture partners and partner relationship characteristics affect joint venture performance. The main findings are as follows. First, the interaction effect between technology that is difficult to codify and frequent direct contact between joint venture partners on joint venture performance was not significant. Additionally, the interaction effect between complex technology and frequent direct contact between joint venture partners was also not significant for joint venture performance. While these findings can be interpreted from several perspectives, they appear to result from the forms and methods of direct contact occurring between partners. Unlike tacit technology transfer between advanced firms with mutually similar knowledge bases, the tacit technology transfer process between developed and developing countries requires more refined and meticulous direct contact approaches between partners. Second, the interaction effect between technology that is difficult to codify and complex technology on joint venture performance with experience sharing between joint venture partners was significant. Therefore, it was confirmed that experience sharing between joint venture partners is an important influential variable for enhancing joint venture performance through tacit technology (codifiability and complexity) in foreign joint ventures in Korea. Third, the interaction effect between technology that is difficult to codify and cultural differences between joint venture partners on joint venture performance was not significant. In contrast, the interaction effect between complex technology and cultural differences showed significant results for joint venture performance. Compared to independent or simple technology transfer, complex technology transfer inevitably expands the scope of communication between partners. In this process, cultural differences between partners—such as different languages and thinking systems—make mutual communication difficult and hinder technology transfer, thereby lowering joint venture performance.