Laser spectroscopy is an emerging technology for measuring nitrous oxide (N₂O) dynamics in the environment, but most studies have focused on atmospheric applications. We have coupled a commercially available cavity ring-down spectroscope (CRDS) (Picarro G5101-i isotopic N₂O analyzer) to an air/water gas equilibration device to collect continuous in situ dissolved N₂O molar concentration and bulk nitrogen isotopic (δ¹⁵N-N₂O) data. The δ¹⁵N-N₂O values measured by the CRDS unit were found to be significantly affected by changes in the mixing ratios of O₂, CO, CH₄, and CO₂. There was also an effect of N₂O mixing ratio on δ¹⁵N-N₂O. A series of equations was developed to correct for the matrix effect of O₂ and the spectral interference by CH₄. Chemical traps effectively prevented interferences by CO and CO₂. The maximum corrections required for N₂O mixing ratio and O₂ matrix effects, were 1‰ (at a mixing ratio of 1.2 ppmv), and 11‰ (at 0% O₂content), respectively. The CH₄ correction only became important at mixing ratios greater than 500 ppmv (>0.5‰). Measurements of N₂O molar concentration and δ¹⁵N-N₂O from the CRDS isotopic N₂O analyzer were similar to those measured with isotope ratio mass spectrometry. We demonstrated the utility of the laser-based system with field deployments in three estuarine tidal creeks in subtropical Australia. Future work in this field should focus on the application of the laser-based system to the measurement of N₂O isotopologues in aquatic habitats, allowing for further constraints to be placed on the pathways of N₂O cycling in aquatic system.