The binding interactions of an anionic surface active ionic liquid (SAIL) 1-butyl-3-methylimidazolium dodecylsulfate [C4mim][C12SO4] with cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDAC) in aqueous media have been critically assessed using multitechnique approaches, viz. conductometry, tensiometry, fluorimetry, dynamic light scattering, rheometry, and turbidity. A strong complex formation has been observed between PDAC and [C4mim][C12SO4] at the air-solution surface. At higher concentration of SAIL, [C4mim][C12SO4] interacts with PDAC to form [C4mim][C12SO4]-PDAC networks that precipitate out in bulk. The size determination measurements, i.e., DLS data, prove that the PDAC chains compress prior to the cmc and spread out after cmc due to interactions with SAIL. Fluorescence measurements endow aggregation number of SAIL with or without PDAC. The surface and thermodynamic parameters of micellization have been obtained for all the systems. This investigation gives information about the forces leading to the complexation between PDAC and [C4mim][C12SO4].