This study investigated the effects of graphic organiser and gender on students' academic achievement in algebraic word problem. Three research questions and three null hypotheses were used in guiding this study. Quasi experimental research was employed and Non-equivalent pre and post test design was used. The study involved the Senior Secondary School 2 (SS2) students in Lagos state. The sample comprised of 40 respondents distributed across three treatment groups [13 in Experimental group 1(E1), 12 in Experimental Group2 (E2) and 15 in Control group (C)]. The experimental groups were taught using the graphic organiser while the control group was taught using conventional teaching approach. A Word Problem Achievement Test (WPAT) was used to collect data for both the pre and post tests. The WPAT was administered to all 40 respondents in the three groups, first as pre-test and after treatment as post-test. Mean and standard deviations were used to answer the research questions while ANCOVA and multiple comparisons were used in testing the three null hypotheses. The results of the analysis indicated that (i) the experimental groups performed better than the control group (ii) the treatment appeared to be more effective among male students than their female counterparts (iii) the main effect of treatment was significant and (iv) the main effect of gender as well as the interaction effects of treatment and gender were not statistically significant.