Both sketching and self-explanation are widely believed to be effective for problem-solving in science learning. However, it is unclear which aspects of these strategies promote learning and how they might interact. Compared to a read-only baseline, we examined the impact of instructing 11-year-old students to solve science problems to sketch, self-explain, or both. Problems were either high spatial or low spatial. We coded elements and relations in their sketches and think-alouds. Self-explanation led to greater accuracy on problems, but only when used alone. Sketching had no effect, although showing more elements and relations in sketches was associated with higher accuracy and occurred more often for high spatial problems. Students may be more comfortable with self-explanation than with sketching and require encouragement or specific instruction to use sketching routinely for the benefits hypothesized to be associated with sketching to appear.