This study assesses environmental knowledge of some selected secondary school students in Katsina, Nigeria. Three representative schools out of total 39 were selected for the purpose of this study. These are (i) Ulul Al-Bab Science Secondary School (Co-educational School, both girls and boys), (ii) Government College, Katsina (Boys only school) and (iii) Government girls college Katsina (Girls only school). 150 students (25 students per each of levels 1-6 of secondary education) were sampled in each of the three selected schools. The selected students were issued with the prepared questionnaire addressing some key issues that probe students’ depth of knowledge of environmental problems, their consequences and solutions of solving them. ANOVA statistical test was used to test for significant variation in the level of environmental knowledge of the students within the individual schools studied in order to identify the extent to which variation in levels of study (i.e. age-grade) on environmental knowledge level of the students. The same test was also used to test for significant difference in the environmental knowledge of the students between different schools in order to determine the effect of variation in gender characteristics on the knowledge level. The results obtained indicate in general that the secondary school students in the town display medium to high level of knowledge on the causes, consequences and solutions of environmental problems, but gender and level of study have generally significant influences the environmental knowledge levels of the students. Appropriate recommendations were made to help improve the level of student’s knowledge of environmental issues in the area.