Restaurants are key venues for reducing sodium intake in the United States but little is known about consumer perceptions of sodium in restaurant foods. This study aimed to fill this gap by examining the accuracy of consumer estimates of sodium in restaurant meals. In 2013 and 2014, meal receipts and questionnaires were collected from adults and adolescents dining at six restaurant chains in four New England cities. The sample included 993 adults and 794 adolescents. Diners were asked to estimate the amount of sodium in the meal they had just purchased. Mean (SD) actual sodium content of meals was 1292 mg (970) for adults and 1128 mg (891) for adolescents. One-quarter of diners were unable or unwilling to provide estimates of the sodium content of their meals. Of those who provided estimates, 90 percent of adults and 88 percent of adolescents underestimated sodium in their meals, with adults underestimating sodium by a mean (SD) of 1013 mg (1,055) and adolescents underestimating by 876 mg (1,021). Respondents underestimated sodium content more for meals with greater sodium content. The study also found significant differences in sodium estimation by chain. Education about sodium at point-of-purchase, such as provision of sodium information on restaurant menu boards, may help correct consumer underestimation, particularly for meals of high sodium content.