This study aims to investigate the effect of employing self-explanation strategy with worked examples on university students' skills in applying decision rules, on the retention of these skills, and on the cognitive load in an online learning environment. The study was designed as a quasi-experimental study with pre-/post-test and control group. A total of 56 juniors from the department of Computer Education and Instructional Technologies in the faculty of education at a state university during the 2015-2016 academic year participated in the study. Two online learning environments to teach decision rules were designed based on worked example method. The participants were assigned to an experimental group (n = 28) with self-explanation strategy and a control group (n = 28) without self-explanation. The data for this study were collected using the "Personal and Academic Information Form", the "Applying Basic Mathematics Literacy Skills Test for Adults", the "Cognitive Load Rating Scale" and the "Test of Skills of Applying Decision Rules". The results of the study showed that the online learning process based on the worked examples with self-explanation caused a significant change in the learners' skills of applying decision rules. It was further determined that the experimental group, which made self-explanation, had higher cognitive load scores on the decision rules application questions. All the students exerted higher cognitive efforts on the decision rules, which were labeled as either complex or hard. In summary, it can be concluded that while the online learning environment based on worked examples with self-explanation improved the learners' skills of applying decision rules and increased their cognitive load, it did not have an effect on their retention performance.