Background: Chile's landmark food labeling and advertising policy led to major reductions in sugar purchases. However, it is unclear whether this led to increases in the purchases of nonnutritive sweeteners (NNS). Objectives: The objective of this study was to assess the changes in NNS and caloric-sweetened (CS) products purchased after the law's first phase. Methods: Longitudinal data on food and beverage purchases from 2,381 households collected from January 1, 2015 to December 31, 2017, were linked to nutritional information and categorized into added sweetener groups (unsweetened, NNS-only, CS-only, or NNS with CS). Logistic random-effects models and fixed-effects models were used to compare the percentage of households purchasing products and the mean volume purchased by sweetener category to a counterfactual based on pre-regulation trends. Results: Compared with the counterfactual, the percentage of households purchasing any NNS beverages (NNS-only or NNS with CS) increased by 4.2 percentage points (pp) (95% CI: 2.8, 5.7; P < 0.01). This increase was driven by households purchasing NNS-only beverages (12.1 pp, 95% CI: 10.0, 14.2; P < 0.01). The purchased volume of beverages with any NNS increased by 25.4 mL/person/d (95% CI: 20.1, 30.7; P < 0.01) or 26.5%. Relative to the counterfactual, there were declines of -5.9 pp in households purchasing CS-only beverages (95% CI: −7.0, −4.7; P < 0.01). Regarding the types of sweeteners purchased, we found significant increases in the amounts of sucralose, aspartame, acesulfame K, and steviol glycosides purchased from beverages. Among foods, differences were minimal. Conclusions: The first phase of Chile's law was associated with an increase in the purchases of beverages containing NNS and decreases in beverages containing CS, but virtually no changes in foods.