There has been a trend in recent years about discovering the effectiveness of implementing different designs of blended learning, in different learning tasks, different learning outcomes, and for different students. This research aimed at discovering the effectiveness of integrated design and sequential design of blended learning of Informatics Subject Matter in developing female secondary school students’ informatics cognitive achievement and achievement motivation—as in the research limitations. Developmental research method was implemented using quasi-experimental two experimental groups design of (22) female students in each group with pre and post tests. Cognitive knowledge aspects were derived through content analysis of the two Units “Advanced Web Concepts” from the Informatics Subject Matter, Instructional design standards list was developed for the two designs, The two blended learning designs were developed through implementing the Elgazzar (2014) ISD model for that Unit in accordance to those standards, two research tools were developed and approved for validity and reliability: Cognitive Achievement test and Achievement Motivation Scale. Research sample of (44) female students was selected and divided to two equal groups and randomly assigned to the research groups according to the specified experimental design. Research experiment was carried out by the first author with the pre and post implementations of the two research tools. Suitable statistical procedures were implemented to test the research hypotheses. Results reveal that there are significant differences at (α ≤ 0.05) among means of pre-post Cognitive Achievement test and Achievement Motivation scores of the two groups. Results also reveal that there aren’t significant comparative differences between means of posttests of Cognitive Achievement test and Achievement Motivation scores of the two designs of blended learning. So, the answer of the question: Is there any comparative Effectiveness between the two designs in Developing Cognitive Achievement and Achievement Motivation among Kuwaiti Female Secondary School Students? Is there isn’t any comparative effectiveness. Research report contains Tables, Figures, and References as well as lists of Recommendations and further researches.