In the highly dynamic, competitive, complex and ‘knowledge intensive’ modern economy the exploitation and management of external knowledge has become of critical importance for the success of firms, and this has led to increasing interest of both researchers and practitioners in the concept of firm’s absorptive capacity (ACAP). It has been recognized that information and communication technologies (ICT) can be quite useful for the improvement of firms’ ACAP. Some empirical research has been conducted in this direction, which however has not examined the role from this perspective of the most important ICT investments of firms: the different types of enterprise systems (ES) implemented by firms increasingly, which become critical infrastructures of their operation. This paper contributes to filling this research gap, by presenting an empirical investigation of the effects of the five most important and widely used types of enterprise systems (ERP, CRM, SCM, business intelligence/business analytics and collaboration support systems) on the ACAP of Greek firms. It is based on data collected through a survey from 122 Greek firms from both manufacturing and services sectors, which are used for the estimation of regression models of firm’s ACAP. It has been concluded that the use of three of the above types of ES, the ERP, the CRM and the business intelligence/business analytics ones, have positive effects on firm’s ACAP, which concern mainly two of its dimensions: the internal diffusion and analysis of external knowledge, and also the assimilation/integration in the knowledge base of the firm.