Abstract: The study investigated the principals’ assessment of chemistry teachers’ effectiveness in teaching chemistry in Federal Capital Territory (FCT); Abuja. The sample consisted of sixty-six (66) principals of senior secondary schools purposely selected from six (6) Local Government area councils. A 21 – item on principals’ assessment of chemistry teachers’ effectiveness questionnaire (PACTEQ, r= 0.82) was developed for data collection. Frequencies, percentages, mean and standard deviation were used to analyse the research questions, while t – test was used to analyse the hypothesis at 0.05 alpha level. The results show that chemistry teachers do not use variety of teaching methods, relevant instructional materials and appropriate evaluation techniques in teaching chemistry. There were no improvisation of the needed instructional materials and majority of the teachers had negative attitudes toward their work. It was also found that there is significant difference in the mean scores of private and public principals on their assessment of the chemistry teachers’ effectiveness in teaching chemistry in favour of private secondary schools. Recommendations were made; to include that secondary school principals should on regular basis, organise in – house training programmes on the use of teaching methods, instructional materials, evaluation techniques, etc for their teachers.