Urban flânerie as one of the forms of lived human experience in public spaces goes beyond physical displacement and encompasses perceptual, social, and existential dimensions, and can be understood as a mode of being in the city. Despite the expansion of studies related to public spaces and urban behavior, the concept of flânerie in Iranian cities has been less frequently examined from an ontological and lived-experience perspective. Accordingly, the present study aims to provide an ontological analysis of the experience of flânerie in Iranian cities and to explain how it emerges within public spaces by examining its bodily, mental–perceptual, and spiritual–existential dimensions and their relationship with urban spatial qualities. This research adopts a qualitative approach within an interpretivist–constructivist paradigm. Data were collected through in-depth semi-structured interviews, non-participant field observations, and analysis of spatial narratives of citizens in different cities of Iran. Sampling was conducted purposively and theoretically, and data were analyzed using thematic analysis in three stages of open, axial, and selective coding. The findings indicate that the experience of flânerie in Iranian cities has a multi-layered ontological nature, articulated through three core themes: “being-in-motion,” “stillness within movement,” and “existential reading of the city.” Moreover, a three-dimensional model of flânerie was extracted, comprising bodily, mental–perceptual, and spiritual–existential dimensions. The results also show that historical urban fabrics, traditional bazaars, pedestrian streets, and green urban spaces have the highest capacity for deep flânerie experiences. Ultimately, the findings suggest that flânerie in Iranian cities represents a meaningful way of inhabiting urban space, emerging from the interaction between spatial qualities, human experience, and processes of meaning-making; therefore, urban public space design should move beyond purely functional approaches and provide conditions for movement, pause, exploration, social interaction, and the experience of meaning.