Quality of life and self-efficacy assessments are increasingly applied in research with type 2 diabetes mellitus patients due to the impact of the disease on their lives. This study aimed to describe the quality of life and self-efficacy in type 2 diabetes mellitus patients and describe the association of quality of life and self-efficacy with demographic, metabolic, and clinical variables. This is a secondary data analysis from a cross-sectional study: “Metabolic control in patients with type 2 diabetes mellitus in a public hospital in Peru: a cross-sectional study in a low-middle income country”. Data were obtained by standardized interviews and evaluation of medical records. The evaluation tools used were the Diabetes 39 questionnaire (D-39) to measure the quality of life and the General Self-Efficacy scale (GSE) for self-efficacy. The median scores of the D-39 and GSE were 34.6 and 34, respectively. The D-39 dimension with the highest score was “anxiety and concern.” Better quality of life was associated with being older than 65 years old, not having complications, and the absence of depression. No significant association was found between self-efficacy and the quality of life score. Results suggest patients with type 2 diabetes mellitus have a poor quality of life. Patient-centered strategies for type 2 diabetes mellitus care must consider these psychosocial factors to improve disease control and quality of life. © 2021, Medwave Estudios Ltda. All rights reserved.