Fish oil has been shown to have a variety of health benefits, yet the oil’s component polyunsaturated fatty acids are highly prone to oxidation. In this manuscript, methods to study fish oil oxidation using low-field ¹H nuclear magnetic resonance (NMR) spectroscopy were investigated. Fish oil samples in open and closed vials were stored at 25 and 40 °C for 26 days, and signals corresponding to triglycerides and oxidation products were identified and monitored over time. Linear and partial least squares regression (PLSR) were used to model common oxidation metrics, peroxide value and p-anisidine value, and predict sample age. Low-field NMR yielded spectra with lower resolution compared to high-resolution spectra; however, regions corresponding to parts of triglycerides and oxidation products did show meaningful trends, with triglyceride signals generally decreasing and oxidation signals increasing over time. While both model types were effective, linear regression results better summarized the variability of the data, leading to successful predictive models of oxidation metrics compared to PLSR. This study provides preliminary evidence that low-field NMR can be used as a rapid method to assess fish oil oxidation, but more data would be needed to apply this model to other oil samples.