The present study investigated the association between eating frequency (EF), diet quality and nutritional status of fifty-five women with breast cancer (BC) undergoing chemotherapy (CT), with three follow-ups, before the first cycle (T0), after the intermediate cycle (T1) and after the last cycle of CT (T2). Dietary data were obtained by nine 24-h dietary recalls (24HR), and the Brazilian Healthy Eating Index Revised (BHEI-R) was used for qualitative analysis of diet. The average EF was established by adding the number of daily eating episodes in the three 24HR of each time. Anthropometric variables were obtained at three times. Women who reported higher EF (equal to or above median value (T0 and T1: 4·67; T2: 4·33 eating episodes)) presented better anthropometric parameters, in T0 and T1, as well as higher scores for BHEI-R specific groups and BHEI-R Total score in T1 and T2. In generalised linear models, the continuous variable EF was negatively associated with all the anthropometric variables in T0 and with the waist:height ratio in T1. There were positive associations for the BHEI-R groups at the three times: Total Fruit; Whole Fruit; Total Vegetables; Dark Green and Orange Vegetables and Legumes. At T1 and T2 the EF was positively associated with the BHEI-R Total score, and also with Whole Grains in T1. The results suggest that a higher EF was associated with a better diet quality during CT in women with BC. In contrast, an inverse association was observed between EF and anthropometric parameters before the first cycle of treatment.