This study evaluated the effect of students' academic achievement on identified difficult concepts or topics in Senior Secondary School Biology in Delta State, Nigeria. The study was quasi-experimental and the design was a 2X2 factorial non-randomized pretest-posttest control group design. The sample was drawn from intact classes from four coeducational schools located in urban and rural centres in Delta Central Senatorial District. A total of 160 male and female students were used in the study. The sample were got using purposive sampling technique. The instrument for the study was designed by the researchers and tagged Biology Achievement Test (BAT). This was validated by experts and Kuder-Richardson formula 21 was used for the reliability estimate and this yielded 0.71 alpha. This was tested at 0.05 significant level. The methods used for evaluating the students was Concept-mapping and the Regular Teaching Methods, as experimental and control groups respectively. The results showed that students perceived some topics like Hereditary, Genetics, Ecology as difficult while it was found out that gender (male and female sex) and school location (urban and rural) had no effect on difficult concepts in Biology. Based on these, recommendations were made; such as innovative teaching strategies like concept mapping be used in our classrooms.