Childhood cancer survivors (CCSs) are at increased risk of developing chronic health conditions. This may potentially be reduced by a balanced diet. We aimed to compare dietary intake and diet quality using the Alternative Healthy Eating Index (AHEI) of adult CCSs and the general Swiss population. A food frequency questionnaire (FFQ) was completed by CCSs with a median age of 34 (IQR: 29-40) years. We compared dietary intake of 775 CCSs to two population-based cohorts who completed the same FFQ: 1276 CoLaus and 2529 Bus Santé study participants. CCSs consumed particular inadequate amounts of fiber and excessive amounts of sodium and saturated fat. Dietary intake was similar in CCSs and the general population. The mean AHEI was low with 49.8 in CCSs (men: 47.7, women: 51.9), 52.3 in CoLaus (men: 50.2, women: 54.0), and 53.7 in Bus Santé (men: 51.8, women: 54.4) out of a maximum score of 110. The AHEI scores for fish, fruit, vegetables, and alcohol were worse in CCSs than in the general population, whereas the score for sugar-sweetened beverages was better (all p < 0.001). Diet quality at follow-up did not differ between clinical characteristics of CCSs. Long-term CCSs and the general population have poor dietary intake and quality in Switzerland, which suggests similar population-based interventions for everyone.