Spatial visualization ability is an important factor in a child's cognitive development. Its development is affected by numerous factors such as general intelligence, problem-solving skills, gender, playing building games, experience with engineering drawing and 3D modelling, etc. The study aimed to explore how engineering 3D modelling with SketchUp computer programme affects the development of students' spatial thinking and visualization in consideration of previous experience with 3D modelling and students' grades in Technics and Technology. The study included 166 11-14-year-old students who were assigned to an experimental and a control group. A pre-and post-test were applied for initial and final testing. To test students' spatial visualization abilities, an experimental tool with the following elements was assembled: Picture Rotation Test, Form Board Test, The Punched Holes Test, Differential Aptitude Test: Space Relations, The Surface Development Test, Mental Rotation Test, Purdue Spatial Visualization Test: Rotations. The experimental group was included in 30-h training in 3D modelling with SketchUp. The results have shown an excellent response of students in the experimental group to the training and confirmed the expectations concerning the improvement of spatial visualization abilities of these students irrespective of their previous experience and school grades in Technics and Technology. The study has shown that introducing spatial modelling with SketchUp in early technics and technology education enables more effective development and improvement of children's spatial visualization ability skills.