There is a lot of emphasis on secondary education in Nigeria since it is the stepping stone between elementary school and college and experience has demonstrated that an employee's effectiveness is affected by his or her rapid and timely promotion. This study investigated the correlation between variables of conditions of service and teacher effectiveness in Ekiti secondary schools. The descriptive survey research design was adapted in the study. A total of 420 respondents were chosen from 20 public secondary schools in Ekiti State using proportional and purposive sampling technique. Conditions of Service Questionnaire” (CSQ) and was administered on the teachers and the second one tagged “Teachers’ Effectiveness Questionnaire” (TEQ) were the self-designed questionnaires for the study. The instruments were screened by experts in educational management and others specialists in the fields of tests and measurement, to confirm their validity. The test re-test approach was used to assess the instruments' consistency. Both descriptive and inferential statistics were used to assess the data collected for the study. Pearson Product Moment Correlation (PPMC) was used to test the hypotheses at 0.05 level of significance. The findings revealed a significant relationship between salary and teacher effectiveness (r-cal 0.632 p=0.000), promotion and teacher’s effectiveness (r-cal 0.374 , p=0.000), and training and teacher effectiveness(0.436, P=0.000). In conclusion, salary, promotion, training, and staff welfare were important variables contributing to teacher effectiveness. It was recommended among others that Governments at all levels should prioritise providing teachers with a welfare package since doing so will encourage them to give their all in the classroom, which will raise student achievement and teacher effectiveness. Keywords: Teacher, Service Condition, Effectiveness, Secondary Schools,