The World Health Organization (WHO) recommends reducing free sugars to less than 10% of total energy intake (TEI) due to their potential implications in weight gain and dental caries. Our objectives were to (1) estimate the intake of total, added, and free sugars, (2) define the main sugar sources, and (3) evaluate the adherence to sugar guidelines. The first national nutrition survey 2014–2015 included non-institutional adults aged 18–75 years. Diet was assessed with two non-consecutive 24-hour dietary recalls in 2057 participants. Added and free sugar content was systematically estimated by two dietitians using available information from the manufacturer and/or standard recipe/composition. Usual daily intake distributions were modeled and weighted for sampling design, non-response, weekdays, and seasons. Total, added, and free sugar intake was respectively 107 g (±44), 53 g (±36), and 65 g (±40), representing 19%, 9%, and 11% of TEI. Sugar consumption was higher among younger adults and lower among people living in the Italian-speaking region. The three main food sources of free sugars were: (1) sweet products (47% of total free sugars), in particular sweet spreads (15%) and cakes/cookies (11%); (2) beverages (29%), mainly fruit and vegetable juices (13%), and sugar-sweetened beverages (12%, but 20% in younger adults); and (3) dairy products (9%), with yogurt accounting for 6%. Respectively, 44% of women and 45% of men had free sugar intake below 10% of TEI. Of people aged between 18–29, 30–64, and 65–75 years, 36%, 45%, and 53% had free sugar intake below 10% of TEI, respectively. The prevalence of Swiss people with free sugar intake that was <5% of the TEI was 8%. Adherence to the WHO recommendations guidelines was generally low in Switzerland, particularly among young adults, and in line with other high-income countries.