This study investigated the use of portfolio assessment technique in teaching map sketching and location in geography in Jos, Nigeria. It adopted a quasi-experimental design. Two schools were selected using a table of random numbers from a population of 51 schools in Jos South and assigned to each of experimental and control group. The experimental group consisted of 49 students while the control group had 52 students. Three hypotheses were formulated for the study. Hypotheses one and three were tested using t-test for correlated samples statistics while t-test for independent samples statistical technique was employed in testing hypothesis two. The instrument used for data collection was a Geography Achievement Test (GAT). The two groups were given a pre-test after which the experimental group was taught map sketching and location using portfolio assessment technique while discussion method was employed to teach the control group. The same test was later administered on the two groups. The findings of the study revealed that portfolio assessment helped in improving students' performance in map sketching and location, where the experimental group recorded higher mean gain scores of 33.32 as against 1.65 gain scores recorded for the control group. Results of the t-test analysis revealed that a significant mean difference existed between the pre-test and post-test GAT mean scores of the experimental group. Gender was found not to have significant effect on the post-test GAT of the experimental group. The study recommended that teachers and schools should employ portfolio assessment technique in teaching to help improve performance in secondary school geography.