A novel method to quantify 1,4-dioxane in finished cleaning products using headspace gas chromatograph with mass spectrometry (HS GC/MS), single ion monitoring, and a fully deuterated internal standard has been developed. The method generates very linear calibration curves with a R2 of at least 0.99, excellent accuracy with spike/recovery of 97%–102%, and effective precision of 1%–7%RSD for different cleaning products. The method also produces an instrument limit of quantitation (LOQ) of <20 ppb, and sample LOQ of <100 ppb. The method robustness was demonstrated with a ten-lab round-robin exercise that showed that even with some unexpected deviations from the method, excellent analytical results were obtained from the different labs. This new method will be valuable to evaluate consumer products impacted by government regulation to limit 1,4-dioxane concentrations in complex matrices.