"The Regeneration of urban brownfields is currently one of the strategies for densification and urban sustainability. However, as an architectural intervention, it is not an easy task and usually leads to two opposing dilemmas; demolition and/or conservation. This difficulty was observed in the regeneration projects of the colonial military brownfields in the city of Tlemcen, where the actors involved adopted different approaches, some of which damaged the existing architectural heritage and its values. The aim of this article is therefore to analyse the transformation processes of the military brownfields studied and to assess their conservation dimension. The latter is considered to be an indicator that makes it possible, on the one hand, to detect the modality of appropriation of the colonial architectural heritage within the projects analysed and, on the other hand, to assess their sustainability from a heritage perspective. This research was therefore based on the following scientific methods: in-situ observation, historical analysis, comparative analysis and semi-structured interviews. The results obtained for the two main study cases showed that the regeneration of the Bedeau barracks has a higher conservative dimension than that of the African hunter’s barracks and can consequently be considered more sustainable in heritage terms. "