We use an adverse selection model to study the dynamics of firms’ reputations when firms implement joint projects. We show that in the case of joint projects a firm’s reputation does not necessarily increase following a success and does not necessarily decrease following a failure. We also study how reputation considerations affect firms’ decisions to participate in joint projects. We show that a high-reputation partner is not necessarily preferable to a low-reputation partner and, when implementation of the joint project by a single firm is possible, a high-quality partner may not be preferable to a low-quality partner.