This paper explores the moderation effect of knowledge complexity and social integration mechanisms on the relationships between the absorptive capacity (ACAP) components in southern Brazilian firms. Our sample includes 174 ICT firms from ten clusters of technology-based firms located in Southern Brazil. Hypotheses were tested using structural equation modelling (PLS-SEM) supported by the software ADANCO 2.0.1. We found that knowledge complexity matters for absorptive capacity. Depending on knowledge complexity, social integration mechanisms may be both: a bless and a curse for absorptive capacity. Specifically, we found that in the paths from acquisition to assimilation, and from acquisition to transformation, high levels of social integration mechanisms help acquire complex knowledge, but they may constraint the absorption of simple knowledge. Our findings contribute to the KBV of the firm by improving our understanding of the role of knowledge complexity as an antecedent of absorptive capacity’ components. By identifying the role of knowledge complexity on the efficiency of both social integration mechanisms and ACAP, this study brings valuable information to managers of both Brazilian firms and foreign organisations willing to establish their operations in Brazil, for the efficient allocation of firm resources for improving the firm innovative performance.