Blended Learning is mostly understood as the use of resources which combine e-learning with other educational resources. In this study, a blended learning strategy was designed with a variety of factors addressed to create a meaningful learning environment facilitated by a variety of modes, methods and moments through a combination of Objectives (Cognitive, Affective & Psychomotor), Methods (Exploratory, Guided Discovery, Self-paced learning) and Media - Synchronous – (Instructor-led Classrooms, Field visits) and Asynchronous - (Surveys, Web/Computer-Based Learning). The strategy encourages task-based learning which includes specific tasks for the pupil to be completed within a specific time through consequent events which are executed through specific activities. The purpose of the present study was to find out the effect of blended leaning strategy on achievement in Biology and social and environmental attitude of secondary school students of Kerala. Experimental cum survey method was adopted. The basic experimental design adopted was Pre-test, Post-test and Non - equivalent group Design. Survey method was used to find out the social and environmental attitude of secondary school students using attitude scales viz., Social Attitude Scale and Environmental Attitude Scale developed and standardized by the investigator. The findings reveal that Blended Learning strategy is an effective means for enhancing achievement in Biology, for improving Social Attitude and Environmental Attitude of secondary school students.