This study investigated the effects of guided inquiry and concept mapping teaching strategies on biology students academic performance in senior secondary schools of Adamawa State, Nigeria. Five research questions and five null hypotheses guided the study. The study adopted the pre-test, post-test, non- equivalent non randomized control group, quasi-experimental research design involving a 2x2 factorial matrix. The population was 24,960 SS II Biology students. The sample of the study was 165 students (83 males and 82 females) drawn from four intact classes selected randomly from four schools. The instrument for data collected was Biology Performance Test (BPT). Kuder-Richardson formula (KR-21) was used to calculate the reliability of the BPT and reliability coefficient of 0.87 was obtained. The research questions were answered using mean and standard deviation. Analysis of Covariance (ANCOVA) was used to test the null hypotheses at 0.05 level of significance. The findings of the study showed that there was mean difference between scores of students taught with guided inquiry (22.42) and those taught with Lecture method (17.04) in favor of guided inquiry strategy; there was no mean difference between male (26.63) and female (28.54) students when taught using guided inquiry strategy; there was mean difference between scores of students taught with concept map (24.29) and those taught with Lecture method (17.04) in favor of concept map strategy. There was no mean difference between male and female mean scores of male (23.00) and female students (26.00). There was significant difference between guided inquiry teaching strategy and lecture method on students academic performance in biology in favor of guided inquiry teaching strategy (0.00) There was no significant difference between male and female students taught biology with guided inquiry teaching strategy and lecture method (0.90). There was significant difference between concept mapping teaching strategy and lecture method on students academic performance in biology in favor of concept map teaching strategy (0.00) There was no significant difference between male and female students taught biology with concept map teaching strategy and lecture method (0.90). there were no significant interaction effects between treatments and gender on biology students academic performance in biology. It was recommended among others that there is need to encourage teachers to use guided inquiry and concept map teaching strategies in order to improve students academic achievement in biology.