Wittgenstein’s mention of the term “phenomenology” in his writings from the middle period has long been regarded as puzzling by interpreters. It is striking to see him concerned with this philosophical approach, generally regarded as being foreign to the tradition of Russell and Frege, in which Wittgenstein’s thought is taken to have primarily developed. On the basis of partially unpublished material from Wittgenstein’s Nachlass , this thesis provides a reconstruction of the rationale and fate of his peculiar notion of phenomenology, which he developed after his return to Cambridge in 1929. On the one hand, this notion is tributary to Wittgenstein’s longstanding task of the philosophical clarification of language. On the other hand, Wittgenstein’s concern with phenomenology develops against the background of his reconsideration of the resources for clarification provided by his early philosophy. His 1929 paper “Some Remarks on Logical Form” is elucidatory in this respect. The paper expresses a dissatisfaction with the Tractarian account of logical grammar and pleas for a “logical investigation of the phenomena themselves”. This plea echoes Wittgenstein’s conception of a “phenomenological language” in the manuscripts from the same period. The thesis discusses the intricacies of this conception and the reasons for Wittgenstein’s criticisms of it. By contrast to the prevalent view in the secondary literature, the discussion shows that he did not fully endorse for a definite period, and then suddenly abandoned, the idea of phenomenological language. Wittgenstein rather attempts to develop a viable means of clarification and philosophical expression through phenomenological language, while critically exploring the implications and consequences of this attempt at the very same time.