This study focused on “Evaluation of Instructional Leadership Practices of Principals in Nigerian Secondary Schools”. The study was specifically interested in finding out the instructional leadership roles played by secondary school principals in Nigeria. In other words, the study evaluated the opinions of Teachers, Ministry of Education Officials and principals in respect of principals‟ instructional leadership practices in Nigerian secondary schools. The mass failure in examinations, non-coverage of school syllabus, wastage in human and material resources teacher incompetence, examination malpractice, absenteeism and so on were assumed or alleged to be the result of inability of principals to effectively play their instructional leadership responsibilities in their schools. The critical areas examined were curriculum implementation, instructional supervision, staff development, provision and utilization of instructional materials, motivation, maintenance of school physical facilities, institutional planning of academic programmes, delegation of authority and communication network. Nine hypotheses were formulated to find out the significant differences in the opinions of the three groups of respondents. The researcher reviewed relevant literature to establish the theoretical bases for the study. The descriptive and survey methods were adopted for investigations and data collection. Through stratified random sampling technique, twelve states in the six geo-political zones of Nigeria were selected for the study. One thousand, two hundred (1,200) respondents comprising of 960 Teachers, 96 Ministry of Education Officials and 144 Principals were selected as samples. Out of the 1,200 copies of questionnaire designed and administered by the researcher, 900 were filled and returned. The questionnaire as the basic instrument was vetted by experts in Educational Administration and Planning and statisticians and was also subjected to pilot study in Taraba State Secondary Schools. The One Way Analysis of Variance (ANOVA) and Scheffe‟s Post-Hoc test were used to test the null hypotheses. Five out of nine hypotheses were accepted while four were rejected. The four rejected hypotheses were subjected to Scheffe‟s post-hoc test to determine the extent of significant differences in the respondents‟ opinions. The major finding of the research indicated that the instructional leadership role performed by principals showed high level of instructional leadership responsibilities in curriculum implementation, instructional supervision, maintenance of school facilities, delegation of authority and communication network. Furthermore, the study also revealed that principals of secondary schools in Nigeria did not adequately give attention to staff development, provision of school instructional materials . motivation of staff and students and planning of school programmes.. The study also revealed that extra-curricular activities such as sports, clubs, debate and so on were not encouraged and promoted by secondary schools principals in Nigeria. Recommendations such as the need to get firm grip of the school curriculum in order to offer useful advice and assistance to teachers, and the need to develop various motivational techniques such as honours, praise, involving teachers in decision making, open door policy etc and the need to engage staff in several staff development programmes to constantly upgrade their knowledge and skills were offered. Finally, suggestions were also made for further research in the area of improvement in teaching and learning in secondary schools in Nigeria.