In this work, we designed a CG model able to represent the spatial and dynamic properties of the C8S3 cyanine dye. To achieve this, we optimised the atomistic parameters for the aromatic core based on quantum mechanics (QM) calculations and tested their performance on available crystal structures of cyanine dyes. The optimised atomistic parameters were used as a reference for tuning the bonded parameters of a CG model with the latest version of the Martini force field, Martini 3 . Its fastidious parametrization procedure, the flexible mapping scheme and the transferability of the building block approach underlying Martini allowed us to construct an accurate representation of the cyanine dye aromatic core and its side chains. The final CG model was tested in C8S3 self-assembly and preformed nanotube simulations. Our results provide insights on the local and global arrangement of C8S3 molecules inside the aggregates. Furthermore, they provide a template for the aromatic core of similar cyanine dyes, since the same core could be used to study other members of the cyanine dye family. The workflow for constructing similar CG models is described in detail.