This paper aims to present a management model to promote serendipity in technology companies. First, we analyzed six cases of serendipity that had been collected over two years of participatory observation in a Japanese technology company. Evaluating each case from the point of view of collaborative activities, it is revealed that the key factors are different according to the type of serendipity (pseudo or true). For pseudo-serendipity, loose communication or informal exchanges among engineers having similar background knowledge is important. Meanwhile, for true serendipity, it is desirable to show the element technology that is the result of pseudo-serendipity to a gatekeeper operating in subsystems or system hierarchy, and to promote collaborative activities around him/her at its center. A management model that encourages and promotes serendipity based on these factual findings is presented, as well as considering a strategy for effective and successful collaborative activities for gatekeepers.