This study examined how international joint venturing affected firms' learning, knowledge acquisition, and their learning effects. It was found that a firm and her partners within an international joint venture (IJV), having frequent and quality communication each other, eventually lead to increased accumulation of codifible and noncodifiable knowledge. The higher level of transparency between firms, the more codifiable knowledge one firm can access and acquire from the other. In addition, organizational learning positively affects what knowledge can be acquired through launching an international joint venture. This research further showed that the relationship between knowledge protection and its acquisition is moderated by adopted control mechanisms. As expected, knowledge acquisition from IJV partners positively affects a firm's performances in product development, process improvement, and employee capability.