The current study developed an intelligent learning environment for online education of research ethics and investigated how encouragement and warning intelligent feedback influenced learners' engagement (behavioural, emotional, and cognitive) and cognitive load (mental load and mental effort). Participants included 191 graduate students in Taiwan who were randomly assigned into four groups: a non-feedback group, a warning feedback group, an encouragement feedback group, and an encouragement plus warning feedback group. The intelligent feedback was established on the basis of learning analytics from a database of prior learners' online learning of off- or on-task behaviours. The system detected students' sequential behavioural patterns and provided instant intelligent feedback. The results showed that encouragement plus warning feedback caused higher emotional and cognitive engagement, whereas warning feedback led to higher mental load. The study suggests that when designing intelligent learning environments, encouragement, and warning intelligent feedback should be used jointly to enhance the appeal of the learning journey and to boost emotional engagement, thereby increasing students' willingness to learn. It is important to avoid using only warning feedback to reduce interference in learning.