Background: Breast cancer is the most common cancer among females in Myanmar but patients often receive treatment rather late. Delays in seeking treatment of breast cancer for a period longer than 3 months, is associated with lower survival. Hence it is important to find out the causes of the delays so that necessary measures may be implemented with a view to improving treatment outcome. Aim: To explore the delays and barriers to early diagnosis and treatment among the breast cancer patients in Yangon. Methods: A mixed method design. All breast cancer patients (total 104) participated in the structured interview and (16) in the Focus Group Discussion (FGD) sessions. Site at Shwe Yaung Hnin Si Cancer Foundation's Charity clinic from September 2017 to February 2018. Results: Some 32.4% had (patient delay - consulted a medical personnel more than 3 months after noticing signs and symptoms), 19.4% had (general practitioner (GP) delay- to refer to cancer specialist) and 44.4% had (hospital or system delay –i.e., treatment delay after first consultation with specialists). Reasons for patient delay were not knowing that painless small breast lump could be serious (37.5%), socioeconomic constraints (18.8%), too busy working (9.4%) too scared (7.8%) and too shy (4.7%). People living in Yangon had 3.8 times less delay than those living outside (OR 3.8, χ2 = 7.4, P < 0.004); those unemployed were 2.4 times less delay than used (OR 2.4, χ2 = 3.77, P < 0.02); negative attitude toward breast lump and being worried had 8 times less chance of patient delay (OR= 8, χ2=19.9, P ≤ 0.0001). Those who perceived that a painless breast lump was serious are 8.8 times less likely to have patient delay (OR 8.8, χ2 = 3.08, P < 0.001). The odds of having GP delay are 3.2 times higher among those having patient delay (OR=3.2, χ2=5.6, P < 0.02). By FGD most of the survivors revealed reasons for delay which were limited information, economic, use of traditional medicine and sociocultural issues. Conclusion: Lack of knowledge was the highest cause of the patient delay, followed by perception, socioeconomic factors and accessibility to health care and so these need to be overcome. The GP delay and system delay need to be further explored to ascertain the exact causes.