In this study, ethyl cellulose micro/nanocapsules containing linseed oil have been synthesized via emulsification-solvent evaporation method as the main agents for the self-healing properties in smart self-healing coatings. Characterization of micro/nanocapsules core material has been evaluated using Fourier Transform Infrared Spectroscopy (FT-IR). Results obtained revealed that the linseed oil has been successfully loaded into the micro and nanocapsules. Size distribution and average diameter of nanocapsules have been investigated using the particle size distribution analysis method. Results have shown that the synthesized nanocapsules had the average diameters of 472.8 and 78.8nm. The average diameter of microcapsules evaluated 108.4µm, using the optical microscopic images. Morphological characterization of the obtained microcapsules showed that the capsules had spherical shape with smooth and uniform outer shell. In order to produce self-healing coatings, the prepared micro and nanocapsules were individually embedded into the polyurethane resin and applied on carbon steel panels. A coating without capsules has been prepared as the reference sample. The adhesion test results showed that presence of micro/nanocapsules with permeable shell properties enhanced the adhesion strength of the polyurethane coatings due to filling the coating defects by releasing linseed oil. Self-healing performance and corrosion resistance of coatings having the standard cross-cut on them, have been evaluated using electrochemical impedance spectroscopy test at different time intervals using the dry-wet cycles in order to simulate the atmospheric corrosion conditions. Potentiodynamic polarization and linear polarization tests have been performed in 3.5wt% NaCl solution. Test results revealed that corrosion resistance of coatings containing capsules have been increased compare to the reference coating sample. Moreover, the resistance of the reference coating and microcapsules containing coatings decreased with elapsing of time, which was due to corrosive agents’ penetration beneath the coatings. The nanocapsules containing coatings maintained their barrier properties due to their self-healing performance and also their resistance remained stable after a short period. Besides, scanning electron microscopic images of samples showed the healing of the scratches caused by oxidative polymerization of linseed oil. Salt spray exposure test for evaluating corrosion performance of coatings in atmospheric corrosion conditions, confirmed the former corrosion test results. To investigate the delamination resistance of coatings under cathodic protection, the cathodic disbonding test was performed on samples with an artificial defect. Results revealed that the reference and microcapsules containing coatings delaminated after elapsing 192 hours, while nanocapsules containing coatings showed very good delamination resistance and disbonded coating areas around the artificial defects were found negligible after about 500 hours of immersion. The electrochemical impedance tests also revealed the stability in corrosion resistance of the coatings in mentioned time period. According to all characterization tests, nanocapsules containing coatings showed the best corrosion resistance and self-healing performance. Besides, all the studied properties have been improved by decreasing the nanocapsules sizes. Results revealed that self-healing coating containing ethyl cellulose nanocapsules would be a proper coating in atmospheric corrosion conditions, for systems with and without the cathodic protection. Keywords: Self-healing, nanocapsules, microcapsules, ethyl cellulose, permeability, atmospheric corrosion.