Most of the literature on joint ventures (JVs) in developing countries has been viewed from the perspective of the foreign partners, ignoring the strategic imperatives and goals of the host country partners. Additionally, there has been very little research on international joint ventures (IJVs) in Thailand. Therefore, a study of the relationships between bargaining power, trust and culture affecting negotiation behaviour and outcomes (JV performance) could clarify and complement the results of past studies. It could lead foreign and Thai investors to better understand what they should do before and after entering into JVs, so as to achieve an effective performance (outcome), the success of IJV, cost minimization and profit maximization. This study examines the variables mentioned above in the context of service industries (e.g. construction, leasing, gas distribution), within the confines of joint venture theory and negotiation theory. The data was gathered using both questionnaires and in-depth interviews with a number of MDs and senior managers of JV firms. Both Thai and foreign parents were interviewed where possible. The result of the study shows that relationships between bargaining power, trust, culture, negotiation behaviour and performance (outcome) exist. A significant external factor affecting JV performance was also identified. Case studies were used as a research strategy for this study. 'Pattern matching logic' and 'explanation building' techniques were used for the analysis of data. In addition, data display technique was added to offer a clear understanding and picture of the results of the study. Regarding JV management and negotiation, this study demonstrated that each JV partner should pay attention and time to support the development of mutual trust and cultural understanding in order to avoid conflict and enhance a successful JV performance. This study also revealed the effect of bargaining power, trust and culture on JV performance mediated by negotiation tactics. This has received little attention in previous studies.