The study examined the influence of time-of-day of instruction on students' performance in physics.The study was a descriptive research and 578 senior secondary two (SS II) students were randomly selected from twenty co-educational public secondary schools based on the time-of-day physics.Proforma, questionnaire and physics lesson timetable were the instruments used. Percentage was used to answer the research questions raised and the hypotheses were tested with t-test at 0.05 level of significance. The findings revealed that students who received physics instruction at times-of-day akin to their peak time-of-day outperformed those who received the instruction at times other than their peak time-of-day. Gender and score levels influenced the time-of-day of instruction on the performance of students in physics. It was recommended among others that school management, especially of the schools that enrol male students only, should construct the timetable and place physics lessons in accordance with the time-of-day that is congruent to the majority of the students.