Learning to read and write efficiently is of the utmost importance in elementary school. However, writing is frequently difficult and can be demotivating for beginning writers. Fortunately these barriers can be partially alleviated with parental help. Many studies showed that parental involvement influences children's competence and motivation in reading, but little is known about the benefits of parental involvement in writing. We report on an intervention program to promote parental involvement in writing and a test of its efficacy. Forty-eight second graders were randomly assigned to an intervention group (n = 22) or to a waiting list (n = 26). Parents in the intervention group attended the program Cultivating Writing in which they discussed how to better support their children towards writing. Parents also trained an interaction sequence for effectively praising and making suggestions concerning their children's texts. Over 10 weeks, teachers asked students to write four stories as home assignment. While children in the waiting list composed texts alone, children in the intervention group composed texts with their parents. When compared to children in the waiting list, those in the intervention group improved in some transcription measures and wrote longer and better texts. These findings indicate that parental involvement in writing is important and seems effective in fostering children's writing skills.