Whereas origami is said to have pedagogical benefits in geometry education, research is inclusive about its effect on spatial ability and geometric knowledge among preservice teachers. The study investigated the effect of origami instruction on these aspects using pretest posttest quasi-experiment design. The experimental group consisted of 52 students while students in the control group were 42. Paper folding test and mental rotation test were used to assess two subscales of spatial ability of the pre-service teachers and achievement test was also used to assess geometric knowledge for teaching shape and space. Data were analyzed using (M)ANOVAs at 0.05 significance level. The results of univariate ANOVAs show statistical and practical significant effect on spatial orientation and geometric knowledge for teaching, but unpredictably no statistical significant difference in spatial visualization between groups was found. The MANOVA however indicated overall statistically significant difference in posttest mean scores between groups with treatment accounting for 17% of multivariate variance of dependent variable. Implications for adopting origami instructions at the colleges of education were discussed.