The study investigated the relative effects of problem-solving and concept mapping strategies on students’ achievement of some environmental concepts in senior secondary school chemistry. The study also sought to know the moderating effects of students’ gender and verbal ability on students’ achievement in environmental concepts. The study adopted pre-test, post-test quasi-experimental design. The population was made up of all senior secondary school three (SS III) students in the three senatorial districts of Ekiti State. The sample consisted of 164 students of which 89 were males and 75 were females. Two instruments were used in the study. These were Environmental Education Achievement Test (EEAT) (r=0.80) and Verbal Ability Test (VAT), (r=0.89). Data were analysed using ANCOVA and t-test. The results revealed that there is a significant difference in the post test scores of subjects exposed to problem-solving, concept mapping and conventional strategies. The study also showed that there is a significant difference in the achievement scores of male and female subjects exposed to the treatments. It was also depicted that subjects of high verbal ability performed better than those of low verbal ability when exposed to problem-solving and concept mapping strategies. On the basis of these, it is therefore recommended that chemistry teachers should adopt the problem-solving and concept mapping strategies in the teaching of environmental aspects of chemistry to their students.