Since its discovery in 1943, LSD has been used by artists, scientists, and intellectuals, amongst others, to stimulate their creative insights. Federico Fellini, one of the most important film directors in the XX century, used LSD when it was still legal under the guidance of his psychoanalyst during a phase of personal and creative crisis. This article proposes a phenomenological analysis of how his filmmaking and his creativity was enhanced after using LSD in such controlled therapeutic settings, according to four main domains: (a) time, (b) space, (c) body and others and (d) perception of the self. In particular, time flows irregularly and is punctuated by disorienting flashbacks, colours become supernaturally brilliant and detached from objects, sounds pop up independently from any visible source, and human bodies become often deformed, grotesque and caricatural. The boundaries between dream- and reality-worlds also collapses. His films became so distinctive and original that an adjective was coined felliniesque.