Background The competence development of middle-level design managers (MLDMs) is essential since they may encounter the challenge of cultivating competences different from those of practical design. The question of which competences to develop was answered in the prior research on the Competence Model for Design Managers (CMDM). Thus, this study aimed to respond to the question of how to develop those competences, namely, what conditions (influential factors) would be required. Hence, this study firstly identified the IFs on developing design managers' competences in a general perspective. In Study I, the influence level of each IF on the competences of CMDM were examined from the view of Korean MLDMs. In Study II, the detail conditions of IFs were further investigated. Methods The IFs were identified from management literature and adjusted by six design experts. Subsequently, the influence level of each factor on the 26 competences of CMDM were determined through an online survey distributed to 70 MLDMs belonging to in-house design organizations of Korean major corporations. The detail conditions of catalytic factors were investigated though semi-structured interviews with 9 MLDMs. Results From Study I, IFs were classified into two distinct types. First, "enabling factors" primarily influenced the cognitive, functional, and social competences. However, the second type of "'catalytic factors" mainly influenced social and meta-competences. Moreover, the necessity of detail conditions was found only in the catalytic factors. Accordingly, the relation between catalytic factors and competences was investigated in Study II. Particularly, social awareness and the social skills of personality, cultural and social aspects of the work environment had influence on the social-tactical competences. Moreover, personal appreciation for and organizational appraisal of the values and contributions of design managers' invisible works (e.g., managing, directing, and bridging) were essential to motivate MLDMs. Conclusions The findings of the research can make contributions in two ways. First, a professional contribution would be suggesting an appropriate and precise combination of IFs to cultivate certain competences for MLDMs, which could be helpful in designing an action plan. Second, this study may make an academic contribution to the knowledge body of design management by identifying the influential levels of IFs on the competences from the perspective of MLDMs, and by providing the classification of IFs according to the enabling and catalytic factors.