This study aims to evaluate teachers' attitude towards implementation of learner-centered methodology in science education in Kenya. The study used a survey design methodology, adopting the purposive, stratified random and simple random sampling procedures and hypothesised that there was no significant relationship between the head teachers' attitudes, the teachers' attitudes and the level of implementation of Activity-focused methods, Student-centred activities, Experimenting and Improvisation through the Plan, Do, See and Improve (ASEI/PDSI) classroom practices. A sample of 68 head teachers, 147 science teachers and 16 trainers was used for the survey. The study established that majority of the teachers (75%) were partial implementers, and a few (5%) were full implementers. The Chi-square findings for the head teachers were: Biology X[superscript 2] = 72.35>66, Chemistry X[superscript 2] = 69.38>66, and Physics X[superscript 2] = 67.03>66. The teachers were: Biology X[superscript 2] = 55.3429>54, Chemistry X[superscript 2] = 54.4581>48 and Physics X[superscript 2] = 69.4286>58 meaning that they were significant. The conclusion was to reject the null hypothesis, and accept the alternative hypothesis that there is a significant relationship between the teachers' and head teachers' attitude, and the level of implementation of the ASEI/PDSI classroom practices. The study recommended that since the level of implementation was found to be related to the teachers' and head teachers' attitudes towards the innovation, the national Strengthening of Mathematics and Sciences in Secondary Education (SMASSE) inset should then have strategies to bring on board those who still have a negative attitude in order for the implementation to be successful.