Learning Biology helps learners to acquire requisite knowledge in understanding life processes for positive coexistence. In instances where learners appreciate the position of biology in life, they develop positive attitude and this is reflected in their performance. However, in Kenya, most students have continued to register poor performance in biology in national examinations and this has been attributed to negative attitude towards the sciences by most learners. To address this, changes in the educational curricula and teaching methods from the transmission curriculum to a transactional curriculum has been suggested. The changes imply adjustments in the instructional process to include learner centred activities. On the other hand, studies have shown that the attitude of learners towards changes influence the adoptability and workability of the introduced change. This study investigated attitude of learners towards the constructivist instructional approach. The study adopted a cross-sectional survey technique. Data was obtained from four boys', four girls', and four mixed secondary schools with a total of 477 students and were analysed using both descriptive and inferential statistics. The results indicated that learners have positive attitude towards the constructivist instructional approach. Boys obtained a scores of (M=58.30; SD=9.15, N=150) while girls had a score of (M=53.14; SD=8.24, N=146). Based on this finding, it is recommended that instructors adopt the constructivist approach in learning so as to boost the attitude of students towards learning biology. It would also be appropriate for further investigations to be conducted in other fields of science such as chemistry and Physics so as to find out if the constructivist approach would also boost the attitude of students in such subjects. Finally, policy makers in the field of education in Kenya (The Ministry of Education, Science and Technology through the Kenya Institute of Curriculum Development (KICD)) should come up with policies to ensure appropriate learning approaches which foster positive attitude towards learning.