Self-determination theory (SDT) has developed gradually over the last 45 years to become a major theory of human motivation and personality. Philosophical roots of SDT are grounded in organismic theory, SDT assumes that humans are proactive by nature, oriented toward healthy development and are vulnerable to passivity, psychological fragmentation, and interpersonal disharmony, especially when the social surround is not supportive of their inherent growth tendencies. Such a dynamic gives rise to an organismic-dialectic meta-theory. SDT uses the achievements of many other approaches. In the field of psychology of motivation it represents a very successful development of ideas about the cognitive mediation of motivational tendencies developed by J. Rotter, J.A. Atkinson, H. Heckhausen, M.E.P. Seligman, B. Weiner, etc. In the field of personality psychology, SDT is a new, much more empirically grounded stage in the development of the ideas of humanistic psychology. This paper offers a way to rethink SDT from a constructivist perspective. It seems that this approach will allow us to unify the ways of motivation formation using different styles of activity regulation, will make it possible to differentiate various regulatory styles within the style that is called external in traditional SDT and also will provide an opportunity to re-examine the problem of distinguishing between extrinsic and intrinsic motivation. It will eventually expand the explanatory power of the SDT.