This paper aims to propose positive and negative firm competitiveness effects of knowledge acquisition of pertinent, irrelevant and erroneous knowledge based on its distinctiveness, the source of knowledge and the presence of firm complements.;;Aspects of knowledge acquisition from the innovation, knowledge and routines literatures are integrated to create propositions showing the effects of knowledge acquisition on firm competitiveness. Examples from different eras of the automobile industry are used to illustrate the propositions and demonstrate the enduring nature of these issues.;;Various combinations of firm complements and knowledge type and criticality can cause significant competitive effects, such as parity, relative harm and opportunity capture, that managers should be cognizant... of when planning knowledge acquisition.;;Knowledge researchers should use a more integrative, holistic approach concerning firm resources to their empirical studies. This better allows for the competitive effects of interactions between new and existing firm resources to be captured.;;The propositions emphasize the importance of increased managerial attention and understanding of potential problems of new knowledge acquisition. Moreover, managers should pay particular attention to their firm’s existing complements when assessing knowledge acquisition benefits.;;The positive value of firm knowledge receives substantially more research attention than the potential negative effects. This paper identifies the competitiveness effects of acquiring pertinent, irrelevant or erroneous knowledge. Increased attention on the interaction of new knowledge and complements illustrates the positive and negative effects on firms.