Purpose: Children with developmental language disorder (DLD) have persistent language difficulties in complex syntax. To date, few studies have examined the effectiveness of syntactic training focusing on complex grammar, with no existing studies having been done in French. In English, the SHAPE CODING (SC) system, which combines shapes and colors to identify the nature and function of words and sentence types, has been shown to be effective with children and adolescents with DLD. Our study assesses the effectiveness of a French adaptation of the SC methodology on the mastery of three syntactically complex structures: object relatives, accusative clitics and passives. Method: We developed a training protocol, inspired by the SC principles, comprised of 13 sessions of 30 minutes, and compared the ability of 18 children with DLD aged 7 to 11 to produce the target structures before and after syntactic training. Three lists of 12 trained sentences were directly trained whereas three untrained (matched) lists were used as a measure of generalization. An untrained structure was used as a control measure. Results: Comparison of scores, as measured by dedicated baselines, shows that training results in improved performance for all target structures, whereas no progression is observed on control items (verbal inflexions), which are not trained. More specifically, results show an improvement on sentences directly trained during the protocol, but also on new sentences that contain the same target structures, reflecting the generalization of the production of these structures. Conclusion: Findings confirm the effectiveness of an explicit approach in grammar interventions and they provide new perspectives on language therapy dedicated to children with DLD. The implications of the results are also discussed at the individual level.