Density functional theory (DFT) was employed to investigate the sensing behaviour of the neurotransmitter dopamine (DA) when interacting with OH-functionalised copper phthalocyanines (CuPcs) and copper phthalocyanines coadsorbed with iodine (CuIPc), both in gaseous and aqueous media. This study revealed that CuIPc demonstrates a superior capacity for detecting dopamine molecules compared to CuPc. Within these complexes, hydrogen bonds and coordination bonds were observed, with hydrogen bonds playing a pivotal role in the dopamine adsorption process. The enhanced electrical conductivity of the CuPc sheets after iodine adsorption, along with the high adsorption energy of the iodine-coadsorbed CuPc/DA complexes, underscores the significance of iodine in this context. Notably, the utilisation of iodine significantly enhances the sensing response for dopamine. In summary, copper phthalocyanine coadsorbed with iodine has emerged as a promising material for dopamine sensors, offering possibilities for further advancements in this field.