Shyness is the tendency to feel awkward, worried, or tense during social encounters, especially with unfamiliar people. Assertiveness – asking for something you need or saying no to a request – is a skill that is difficult for many people. Play therapy is a method of therapy that uses play to uncover and deal with psychological issues in children and adolescents. This study set out to compare the effectiveness of sandplay and storytelling therapy in shyness and assertiveness of fourth to sixth grade elementary school children in Gonbad-e Kavus in 2017-18 school year. This quasi-experimental study had a pretest-posttest control group design. To achieve the research goals, forty-five students with higher levels of shyness and lower levels of assertiveness were selected and assigned to 3 groups of 15 - 2 experimental groups and 1 control group. The research instruments included Stanford Shyness Survey (1977), the Gambrill and Richey Assertion Inventory (1975), and sandplay and storytelling therapy training packages. At the end of study, the pretest and posttest scores of the three groups were compared and the obtained data were analyzed by multivariate analysis of covariance (MANCOVA). The results showed that sandplay and storytelling therapy were effective in students' shyness and assertiveness. The obtained means also indicated that sandplay therapy was more fruitful than storytelling therapy.