This research paper explores the effectiveness of using mobile technologies to support a blended learning course titled Scientific Research Methods in Information Science. Specifically, it discusses the effects of WhatsApp mobile learning activities guided by activity theory on students' knowledge Management (KM). During the 2014 academic year, the researcher adopted an experimental approach-based comparison between an experimental group (34 students) and a control group (34 students). The learning process of the experimental group was based on continuity between 2 hours of in-class learning and 1 hour of learning activities that were mediated by WhatsApp instant messaging each week. The control group's experience was 100% in-class with no app mediation. The researcher used the t-test to compare the means of the control and experimental groups in the test and the students' attitudes at 0.05 alpha levels. This research paper is useful for exploring the effectiveness of mobile technologies in supporting blended learning courses.