The purpose of this paper is to explain the role that routines play in achieving sustainable organisational ambidexterity in information technology (IT) firms. Our exploratory analysis of four case studies reveals the key importance of routines in setting the context for sustainable ambidexterity. Companies build up contextual ambidexterity through routines derived from normalization of processes, normalization of skills, and normalization of results. The findings of the study show that routines support IT professionals to decide whether to exploit or explore in each particular case. Firstly, the enabling character of explicit routines as a result of the normalisation of work processes and the freedom that IT professionals have when implementing them, allows IT professionals to balance exploitation and exploration. Secondly, companies build up contextual ambidexterity through normalisation of skills. Hence, IT professionals develop embedded implicit routines as a result of training. Thirdly, the findings of the study reveal how routines are settled through the normalisation of results that orientates performance towards satisfying customer demands, as well as supporting professionals in their efforts to balance between exploitation and exploration which is necessary to achieve sustainable ambidexterity in IT firms.