This study aimed to explain factors affecting quality of teaching and determine their impact on teaching quality. The mixed research approach and sequential exploratory strategy of classification model were used to collect the data. The population (qualitative method) consisted of staff at central organization of a technical and vocational university and top technicians and researchers of a technical and vocational university in 2011-2016; they were selected using mixed sampling (homogeneous and snowball) method. The population (quantitative method) also consisted of educational assistants, heads of research and education department, and faculty members in 2016. In qualitative study, the exploratory interviews and semi-structured interviews were used for collecting the data. In quantitative study, the identified categories which were derived from encoding qualitative data were used to create paired comparison questionnaires; they included factors affecting quality of teaching. Using Expert Choice Software, the results were analysed by AHP method. The findings indicated that the contribution of teacher, educational environment, and students were estimated to be 41, 33, and 26 percent, respectively. Among teacher components, the professional skills of teacher (weight 361 out of 1000) was determined to be the most important component; among student components, the academic records and experiences (weight 385 out of 1000) was determined to be the most important component; and among educational environment components, quality of environment and educational conditions (weight 341 out of 1000) was determined to be the most important component.