Suburban infrastructure holds a position of increasing geographic, political and conceptual importance in a rapidly urbanising world. However, the analytical significance of ‘suburban infrastructure’ risks becoming bogged down as a chaotic concept amid the maelstrom of contemporary peripheral urban growth and the explosion of interest in infrastructure in critical urban studies. This paper develops an open and flexible comparative theory of suburban infrastructure. I eschew concerns with definitional bounding to focus analytical attention on the relations between ‘the suburban’ (broadly considered) and multiple hard and soft infrastructures. These relations are captured in two ‘three‐dimensional’ dialectical triads: the first unpacks the modalities of infrastructure in, for and of suburbs; the second discloses the political economic processes (suburbanisation), lived experience (suburbanism) and dynamics of mediation internalised by particular suburban infrastructures. Bringing these conceptual frames together constructs a nine‐cell matrix that: (1) functions as a heuristic device providing conceptual clarity when discussing the suburbanity of infrastructures; (2) promotes comparative analysis across diverse global suburban contexts; and (3) develops tools to foreground the dialectical relations internalised in the concrete sociospatial modalities of suburban infrastructure. The paper shows that suburban infrastructure can only ever be partially suburban as a result of its co‐constituted and over‐determined production. I conclude by suggesting how the proposed approach may be mobilised to reimagine and reclaim suburban infrastructure as a crucial context and vital mechanism underpinning a progressive polycentric suburban spatial polity.