This study is aimed at developing mind mapping strategy to improve the tenth-year students’ writing ability at Madrasah Aliyah (MA) Mambaus Sholihin Gresik and focused on solving the problem of how the students generate and organize ideas for writing a topic. The design of the study is collaborative classroom action research. Both the researcher and his collaborator work together in cyclic activities – planning, implementing, observing and reflecting on the data gained from the teaching and learning process – which runs into three cycles, each of which covers four meetings. The findings show that by implementing mind mapping with the proper model developed, the students’ ability in writing a descriptive text improves. It is indicated by the improvement of the percentage of the students achieving the score greater than or equal to 65 and of the percentage of the students’ involvement in the writing activities during the implementation of mind mapping in the instructional process in Cycle I, II, and III. The improvement of the students’ ability in writing a descriptive text can be reached but it should follow the procedures of the proper model of mind mapping developed.