Abstract: Formal operational stage differs from the previous stages due to the newly acquired ability to think in abstract terms and form hypotheses based on propositions (Inhelder & Piaget, 1958). As the adolescent progresses from early to late stage of development, the knowledge structure becomes more and more integrated in structure. Present study hypothesized that the ability to reason in abstract terms is associated with spatial visualization ability and this association becomes more integrated among late formal reasoners as compared to early formal reasoners. Reasoning of abstraction involves classifying objects or events into problem categories based on their properties. This is followed by making inferences in order to solve the problem which in turn requires visualizing the spatial relations among objects/events. Abstract reasoning thus, requires conceptual knowledge and spatial visualization. Spatial Visualization is the ability to visualize complex spatial relations among the constituent parts of an object and manipulate them in order to predict a possible outcome. To test this hypothesis, data were collected from 71 high school students (Boys=23; Girls=48; Mean age=14.52 years) by administering paper-pencil tests of abstract reasoning and spatial visualization. Results revealed significant association between abstract reasoning and visualization factor, with the association being stronger among late adolescents as compared to early adolescents. Results were discussed in the light of Piagetian theory of formal operational reasoning among adolescents.