Video lectures are being widely used in online and blended learning classes worldwide, and their learning effectiveness is becoming a focus of many educators and researchers. This study examined the cognitive load and learning effectiveness of video lectures in terms of the type of knowledge being taught (declarative or procedural) and instructor visibility. Video lectures with and without an instructor were used to teach each type of knowledge. Sixty Chinese undergraduates were randomly assigned to two of the four lectures. They completed a cognitive load questionnaire and learning tests after viewing the lectures. The results of t-tests revealed that adding the instructor in a video lecture increased learners’ cognitive load only when learning procedural knowledge; adding the instructor only facilitated declarative knowledge learning. The results suggest that the learning effectiveness of video lectures varies depending on the type of knowledge being taught and the presence or absence of an instructor.