Introduction: The aim of this study is to present an intervention program for creative skills development applied to a group of students of lower Secondary Education. Method: This program was applied in a school in Zaragoza (Spain) during the 2008-09 academic year. The study used a repeated-measures, quasi-experimental design with non-equivalent control group. The sample included 48 participants, ages 13-14 (24 experimental and 24 control participants). Three assessments were taken, before and after administering the program: the Torrance Test of Creative Thinking (TTCT) was applied as a pretest and postest in its parallel forms, and the Test of Creative Imagination for Young Children (PIC-J) was applied as a follow-up test to improve the reliability of the intervention. The program consisted of weekly 50-minute structured sessions with their objectives, activities and evaluation criteria. Results: ANOVA results showed that development of verbal and figural creativity in the experimental group was significantly higher (p less than 0.05) than in the control group. Verbal creativity development was higher than the figural. Conclusion: The results of this study suggest that, in order to improve the educational effects of creative skill development, creative development should be incorporated into the objectives through the teaching and learning process of the educational methodology. This aspect highlights the importance of preparing the trainee teacher in creative thinking skills. (Contains 4 tables.)