In this article, we examine the issue of Polish entrepreneurs’ attitudes towards knowledge workers above the age of 65 in the context of pro-social and citizenship behavior. The article was written as part of the diversity management paradigm. Firstly, it presents the existing literature on the subject, and then, we present our analysis on the results of a longitudinal study conducted among 93 entrepreneurs, owners, and co-owners of small and medium enterprises, during 2014 and 2019. During this time, legal regulation took place twice, extending and then shortening the period of obligatory work enabling employees to acquire the right to retire. The study was carried out using a specially developed questionnaire, whose reliability met the requirements of methodological correctness and two other research tools. Positive, neutral and negative attitudes were identified among entrepreneurs’ attitudes towards knowledge workers aged 65+. The research results show a correlation between the attitudes of entrepreneurs in 2014 and 2019, stabilization of these attitudes (in relation positive, neutral and negative attitudes), and their particularly significant relationship with organization-oriented citizenship behavior.