Organizational ability can be defined as the ability to plan ahead and organize behavior across time and space. Students need organizational ability to fulfill some of their tasks inside and outside the school. They need to represent the required sequence of cognitive and psychomotor actions at each point in time, in relation to varied spaces (e.g., bedroom, kitchen) and accessories (clothes, schoolbag, notebooks, food). This study of 114 primary school students investigates the roles of organizational ability and handwriting proficiency in writing performance. In this research study, the Questionnaire for Assessing Students' Organizational Abilities (QASOAT), developed by Lifshitz and Josman (2006), and the Handwriting Proficiency Screening Questionnaire by Rosenblum (2008), were adapted to Turkish and subjected to validity and reliability studies. Narrative and informative texts written by students are used to assess their writing performances. Research findings suggest that there are significant relationships between organizational ability, handwriting proficiency and the students' writing performances. The Structural Equality Model (SEM) shows that organizational ability and handwriting proficiency explain 45% of writing performance.