Abstract. Background: Many Type 2 Diabetes Mellitus (T2DM) patients refuse insulin therapy even when they require this modality of treatment. However, some eventually accept insulin. This study aimed to explore the T2DM patients' reasons for accepting insulin therapy and their initial barriers to use insulin. Methods. This qualitative study interviewed twenty-one T2DM patients at a primary care clinic who had been on insulin for more than a year through three in-depth interviews and three focus group discussions. A semi structured interview protocol was used and the sessions were audio-recorded. Subsequently, thematic analysis was conducted to identify major themes. Results: The participants' acceptance of insulin was influenced by their concerns and beliefs about diabetes and insulin. Concerns about complications of poorly controlled diabetes and side effects of other treatment regime had resulted in insulin acceptance among the participants. They also had a strong belief in insulin benefits and effectiveness. These concerns and beliefs were the results of having good knowledge about the diabetes and insulin, experiential learning, as well as doctors' practical and emotional support that helped them to accept insulin therapy and become efficient in self-care management. These factors also allayed their negative concerns and beliefs towards diabetes and insulin, which were their barriers for insulin acceptance as it caused fear to use insulin. These negative concerns were related to injection (self-injection, needle phobia, injection pain), and insulin use (inconvenience, embarrassment, lifestyle restriction, negative social stigma, and poor self-efficacy), whereas the negative beliefs were 'insulin could cause organ damage', 'their diabetes was not serious enough', 'insulin is for life-long', and 'insulin is for more severe disease only'. Conclusions: Exploring patients' concerns and beliefs about diabetes and insulin is crucial to assist physicians in delivering patient-centered care. By understanding this, physicians could address their concerns with aim to modify their patients' misconceptions towards insulin therapy. In addition, continuous educations as well as practical and emotional support from others were found to be valuable for insulin acceptance. Trial registration. Universiti Kebangsaan Malaysia FF-214-2009. � 2013Abu Hassan et al.; licensee BioMed Central Ltd.