There have been perennial concerns on the low academic performance of students among researchers and other education stakeholders. Innovative teaching strategies have, therefore, gained prominence in the field of mathematics education. The purpose of this study is to investigate the impact of a social constructivist instructional strategy on students’ performance in algebra. The present study is quasi-experimental, and its type is a posttest control group involving 154 secondary school students that are randomly selected across four intact classes. The random selection of students to treatment and control controls is assumed to improve the validity of the results. Two research questions are raised, and two null hypotheses are formulated and tested atp≤0.05level of significance. One research instrument, algebra performance test (APT), was developed, pilot-tested (test-retest reliability coefficient of 0.897), and used to measure students’ performance in both treatment and control groups. The data are analyzed using independent samplet-tests. The findings indicate that there are significant differences in the mean performance scores between experimental (mean = 16.05, SD = 2.74) and control (mean = 11.46, SD = 2.49) groups,t(152) = 10.83,p<0.05. These findings may be interpreted to be evidence of the effectiveness of the social constructivist instructional strategy in improving performance in algebra better than the conventional teaching method. Also, a significant difference exists between the mean performance scores of males (mean = 17.83, SD = 2.82) and females (mean = 14.72, SD = 1.77) in the experimental group (t(80) = 6.11,p<0.05). Thus, the effect of the social constructivist instructional strategy on students’ performance in algebra is gender-sensitive. Based on these findings, some recommendations are made to students, teachers, parents, administrators, and other stakeholders.