This study investigated artificial intelligence in secondary education with emphasis on teacher perceptions, instructional decisions, and integration challenges among teachers in Niger State, Nigeria. The study adopted a descriptive survey research design. The population comprised teachers in public secondary schools in Niger State, while a purposive sample of 60 teachers (35 males and 25 females) was selected for the study. Data were collected using an instrument titled Artificial Intelligence Integration Questionnaire (AIIQ). The instrument was validated by experts in science education, while reliability coefficient was 0.86 using Cronbach's alpha, indicating high internal consistency. Three research questions and three corresponding null hypotheses guided the study. Descriptive statistics of mean and standard deviation were used to answer the research questions, while inferential statistics of Independent Samples t-test were employed to test the hypotheses at the 0.05 level of significance. Findings revealed that teachers generally held positive perceptions toward the use of artificial intelligence in secondary education, acknowledging its potential to improve lesson planning, assessment, and personalized learning. The results also indicated that AI tools moderately influenced teachers’ instructional decisions, particularly in content delivery, students and assessment. However, significant challenges were identified, including limited technical skills and insufficient professional training in AI applications. There was no significant gender difference in teachers’ perceptions of AI integration, but a significant relationship was observed between teachers’ level of AI awareness and their instructional decision-making practices. Although, teachers in Niger State recognize the pedagogical value of artificial intelligence, several structural and professional barriers hinder its effective integration in secondary education. It was recommended that government and educational stakeholders develop clear policy guidelines to support the responsible and effective use of artificial intelligence in teaching and learning.