Self-efficacy (SE) is a key factor of the teaching-learning process success. While literature on SE and its dimensions is rich in the field of education, still there is a lack of studies aiming to explore teachers’ SE in contrast with their actual teaching skills and their characteristics. For this reason, this study aims to respond to the following research questions: are there differences between perceived SE and actual teaching performance in preschool and primary school teachers? Which sources of SE can be considered as significant predictors of teachers’ SE? This work employs a quantitative approach based on the observational method. Teacher Sense of Efficacy Scale and classroom observation frameworks were used to collect data from a sample of 24 teachers. Results show that there are high inconsistencies between self-judgments and actual teaching performance (p > .05). Experienced and medium experienced teachers show higher scores than novice teachers in several dimensions of SE (p < .05). However, teachers’ educational background is not significantly correlated with their SE (p > .05). Resource support is found as the only significant predictor of SE in our sample of teachers (p < .001; p 2 = .733). Our research suggests that teachers may have a distorted perception of their in-class performance, which could drive to lower quality of the teaching-learning process. Therefore, in the future, professional training programs should focus on promoting a more realistic understanding and awareness of teachers’ actions in the classroom as the first step of any intervention aiming to increase teaching quality.