In the present research, the performance of a polyurea based dual capsule self-healing system with the ability to work underwater was investigated in epoxy anti-corrosion coating. Moreover, the relationship between healing reaction kinetics and crack formation rate were studied through change in the molecular characteristics of healing agents. Microcapsules were prepared through the electrospray method by using Poly (Styrene-co-Acrylonitrile) polymer as shell material. The dual capsule system included one component with the amine functional group and the other component with the isocyanate functional group, which were encapsulated separately. The amine healing agent was modified by catechol unit present in the dopamine molecule to enhance the underwater self-healing performance. Fourier Transform Infrared Spectroscopy, Thin Layer Chromatography, and Nuclear Magnetic Resonance Spectroscopy confirmed successful modification reaction. Moreover, the molecular weight and functionality of the amine healing agent were varied to investigate their effects on the efficiency and kinetics of the healing reaction. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed spherical core-shell morphology for both amine and isocyanate-containing microcapsules which were prepared at optimum electrospray conditions. The average diameter of microcapsules was measured to be 0.93± 0.55 ?m, 1.01± 0.29 ?m, 0.81± 0.34 ?m, and 1.21± 0.68 ?m for Jeffamine D230, Jeffamine D400, Jeffamine T403, and Coronate 1391 isocyanate, respectively. It was also measured 0.84± 0.60 ?m for the microcapsules containing catechol modified amine. Thermogravimetric analysis (TGA) results confirmed the successful encapsulation of all core materials with a high encapsulation process yield of 71.2% , 72.7%, 69.7%and 68.1% for Jeffamine D230, Jeffamine D400, Jeffamine T403, and Coronate 1391 isocyanate, respectively. It was also determined to be 78.7% and 81.8% for the core materials including 10 wt% and 40 wt% of catechol modified amine, respectively. The self-healing anti-corrosion coatings were prepared by mixing the prepared core-shell microcapsules into the epoxy resin and applying them as a coating on the steel substrate. Conical mandrel bending test, adhesion strength, gloss test, and electrochemical corrosion evaluation experiments were used to evaluate the properties of the prepared coating. Electrochemical impedance spectroscopy (EIS) confirmed the healing performance of the aforementioned dual capsule system with the highest healing efficiency of 85% for the coating containing 3 wt% of microcapsules (1:1 weight mixture of amine and isocyanate containing microcapsules). According to the EIS results, 73.9% increase in molecular weight of amine healing agent, decreased the total corrosion resistance by 38.4%, while increasing the amine functionality from 2 to 3 (in identical molecular mass) increased it by 78.4%, which indicates the strong impact of the functionality on the efficiency of the healing system. The EIS results also showed that incorporating the modified healing agent improved the healing performance and increased the ultimate healing efficiency in the presence of water. The fatigue test results using tapered double-cantilever beam (TDCB) revealed that the ability of the healing system in reduction of the crack's growth rate, under applied dynamic stress, was not significantly affected by increasing the healing agent's molecular weight, whileincreasing the functionality enhanced thehealing performance. Keywords: Epoxy coating, Self-healing, Electrospray, Core-shell microcapsule, Polyurea