The present study investigated the water mobility in muscle of salted sardines (Sardinella brasiliensis) on different days of storage, by the use of Low-Field Nuclear Magnetic Resonance (LF NMR 1H). The exponential fitting of the transverse relaxation (T2) data revealed three components (three pools): one with a relaxation time of 11.2–17.5 ms; a second with a relaxation time ranging from 35.3 to 44.7 ms and the third with a relaxation time of 161.7–256.5 ms. Conventional physical and chemical analyses revealed changes in the quality of the salted fish during storage. A close correlation was observed between the indication of quality (good, regular and poor) obtained through the physical and chemical parameters analyzed (cooking test, presence of ammonia and hydrogen sulfide), and the relaxation data (NMR) (p < 0.05). The change in water mobility-induced by degradation that occurs during storage of salted fish resulted in changes in component (water pools) values observed by transverse relaxation NMR. These results are relate primarily to protein degradation that occurs during storage of the product, altering the dynamics and organization of water molecules. •We used LF 1H NMR to study changes in the quality of salted fish during storage.•LF NMR can be used to investigate changes in water mobility in the food structure.•The LF NMR indicated that the additive causes changes in the salted-fish muscle structure.•Correlations were found between LF 1H NMR parameters and physical and chemical quality properties.•LF 1H NMR is useful for investigating the distribution of water in salted fish.