: Studies on the effects of non-nutritive sweeteners (NNSs) in pregnant women are scarce are conflicting. A major challenge is to accurately assess NNS intake, especially in countries where many foods and beverages have been reformulated with the progressive replacement of sugar by NNSs, due to the implementation of new nutrition labelling policies for preventing obesity. This study aimed to develop and valid a food frequency questionnaire (FFQ) to examine the intake of NNSs in pregnant women. This questionnaire was tested in 29 women in their eighth month of gestation, compared to a 3-day dietary records (3-DR). FFQ validity was assessed using Spearman´s correlation coefficient, Lin´s concordance correlation coefficient (CCC) and Bland-Altman plots. Spearman correlations between NNS FFQ and 3-DR ranged from 0.50 for acesulfame K to 0.83 for saccharin. The CCC ranged from 0.22 to 0.66. Bland-Altman plots showed an overestimation of saccharin, sucralose and steviol glycosides intake by the NNS FFQ, and an underestimation of acesulfame K and aspartame, compared to 3-DR. Overall, the most frequently consumed NNS was sucralose None of the participants exceeded the acceptable daily intake for any of the NNSs evaluated. The FFQ of NNSs appears to be a reasonably valid tool for assessing NNS consumption in pregnant women.