Pain catastrophizing is a well-known concept in the pain literature and has been recognized as one of the most powerful psychological determinants of negative outcomes for pain problems. However, relatively little effort has been put into developing its theoretical underpinnings. More specifically, the intrinsic function of catastrophizing is not explicitly dealt with in contemporary theoretical models. The aim of this article is to add to existing models by proposing a development of the conceptualization of catastrophizing that stresses its function as an emotion regulator. We argue that catastrophizing can be conceptualized as a form of negative repetitive thinking, which is abstract, intrusive, and difficult to disengage from. It has been argued that repetitive negative thinking is a form of ineffective problem solving that functions to downregulate negative affect and that it can be regarded as an avoidant coping strategy because it impedes processing of emotional and somatic responses. Thus, in our conceptualization, catastrophizing is proposed to be a form of problem-solving behavior that functions to reduce negative emotion triggered by pain, and other related stimuli. Furthermore, we argue that catastrophizing is preferably regarded as a process where cognitions, emotions, and overt behavior are intertwined and not viewed as separate entities. To underscore the latter, we suggest the term catastrophic worry. Our intention with this development of the conceptualization is to give rise to new ideas for research and clinical practice and to revitalize discussions about the theoretical framework around pain-related catastrophizing.