Existing literature suggests that a strong culture is essential to the success of an organisation. However, some researchers have since disputed this claim, arguing that while some strong cultures lead to success, others fail. Examining several examples over time, the so-called “case for a strong culture” presents significant weaknesses. The present study, based on the Competing Values Model, examines the effects of a culture’s strength on the organisational performance in the public sector. A sample of 92 departments of Greek public organisations was examined, of which a total of 424 people responded to an online questionnaire. The participating organisations and their departments range in size, in terms of the number of their staff, from 15 to 54 members, and come from different segments of the public administration. The results showed that there is no relationship between culture’s strength and an organisation’s performance and that strong cultures do not have a significant impact on organisational performance in the public sector. The main objective of this research is to enrich the existing knowledge on the relationship between culture and performance, especially in the area of the public sector, since existing studies mainly focus on culture comparisons between large companies using mainly small samples. This study highlights the importance of culture given the chronic problems of Greek public administration to create public value and to be innovative and effective. The results are also of particular importance for the post-pandemic period indicating the need for major changes and reforms in public administration.