The Relational Needs Satisfaction Scale (RNSS) is an instrument that measures the satisfaction of relational needs. More specifically, relational needs are those that are essential in human relationships and can only be satisfied by an attuned response from another person. The scale was developed according to Richard Erskine’s theory of relational needs, which is based on object relations theory, attachment theory, and transactional analysis. The scale includes 20 items and measures both the general satisfaction of relational needs and five dimensions of relational needs: (1) Authenticity, (2) Support and Protection, (3) Having an Impact, (4) Shared Experience, and (5) Initiative from the Other. The RNSS was originally developed in the Slovenian language and has since been adapted into Bosnian, Chinese, Czech, Spanish, and Turkish, demonstrating strong international applicability and cross-cultural relevance. The results from validation studies in different countries support both the 5-factor and hierarchical model of relational needs, while most studies favored the hierarchical model as more congruent with the theory. All studies found high reliability of the total score, with adequate reliability of the subscales in most studies. Studies of convergent validity showed that satisfaction of relational needs is related to secure attachment, self-compassion, satisfaction with life, well-being, lower subjective distress, and a lower manipulation of others from a false victim position. In the chapter, the authors also present an adapted version of RNSS for measuring satisfaction of relational needs at the workplace (W-RNSS) with good psychometric characteristics. Satisfaction of relational needs at the workplace correlates with higher job satisfaction, motivation and work engagement, and lower burnout. The RNSS and W-RNSS are promising new scales that can be used in different areas of psychological research and practice.