Present study explores the utilization of a host assisted aggregate assembly of a DNA intercalater cationic dye, ethidium bromide (EtBr) with polyanionic macrocyclic host, sulfated cyclodextrin (SCD) as colorimetric and fluorometric dual mode sensor for a cancer biomarker, spermine (Sp). The cationic dye, EtBr at the vicinity of the multi-negative SCD portal experiences strong electrostatic attraction, favoring their aggregation in an end to end fashion. Consequently the solution changes its color from orange to brick red with substantial reduction in the fluorescence intensity. Interestingly, in the presence of multi-cationic Sp, the dye aggregates are dissociated which restores the original color and fluorescence intensity of the dye solution. Such changes in the optical features been calibrated with the added Sp concentration to detect and quantify Sp with an astonishingly low detection limit of 0.28 μM in water, 0.59 μM in a 1 % human serum matrix and 5.9 µM in 10 % urine matrix. Furthermore, the ability of the system to undergo visible colour change enhances its reliability as a dual sensor, functioning as a fluorometric as well as a colorimetric tool for spermine detection with enhanced sensitivity, selectivity and rapid response.