Background: Fear and anxiety can predispose breast cancer (BC) patient to serious consequences including non-adherence to chemotherapeutic agents leading to uncontrolled management. The situation is more complex during Covid-19 pandemic. The purpose of this study was to determine the relationship between fear, anxiety and chemotherapy adherence among patients having breast cancer during COVID-19.A cross-sectional correlational design was used. Sample: A purposive sample of 168 patients having breast cancer was selected. Setting: The study was conducted in the Chemotherapy Department at El Tagamoo El Awal Breast Cancer Hospital Data was collected using three instruments. Instrument one: (a) Structured Interview Questionnaire,(b)Assessment of Fear of COVID-19 Likert Scale and Instrument two: Beck anxiety Inventory (BAI) Likert scale. Instrument three: Chemotherapy Adherence Questionnaire .Results: The higher percentage (59.50%) of patients missed more than 4 cycles of chemotherapy. A strongly positive relationship was found between mean score of anxiety and fear (r=.318**;P=.000) among BC patients. Studied patients had severe anxiety (54.33±8.89), high level of fear mean score (28.43± 4.87) and non adherence to chemotherapy (7.02±1.89).Conclusion: There is a strong positive relationship between fear and anxiety. Chemotherapy adherence among patients having breast cancer during COVID-19 is reduced if patients have high levels of fear and anxiety. Replication of the study in different geographical areas is recommended to generalize the results.