<p>Biodiversity offsetting (BO) is aimed to counterbalance biodiversity impacts from development projects. In Sweden, interest in BO within urban planning has grown since the mid-to-late 1990s, when the approach was first piloted in the municipality of Lomma. Because urban planning often involves non-protected nature, BO is not legally mandated but instead implemented on a voluntary basis. So far, evaluations of outcomes of voluntary BO remain scarce and ambiguous. This study aimed to investigate how BO is implemented in urban areas and how it can be evaluated. Using the Swedish municipality Lomma as a case, we developed an assessment framework – consisting of a document analysis and two types of field surveys, which assessed the implementation degree of BO actions and their biodiversity values, across five detailed development projects. The study revealed an exploitation of nearly 49,000&#xa0;m² vegetation across six biotope types to be compensated for. Planned offsets constituted 33,000&#xa0;m² vegetation across five biotope types and 641 solitary (street) trees. Most of the 32 assessed BO actions were implemented, but several to a lower quantity as stated in the plan, particularly for the biotope types ponds, forests, and meadows. Solitary trees were the prominent BO action type, offsetting various biotopes, i.e., like-for-unlike. The field survey indicated a successful establishment of diagnostic plant species in the offset biotopes. Although they showed lower species richness and diversity – biodiversity relevance and nectar production were comparable or slightly higher than the compared reference biotopes, especially in parks. We suggest that implementing other offset biotopes, rather than predominantly solitary trees, could better enhance the urban habitat diversity. Finally, the study emphasizes the importance of documentation and transparency to enable adequate evaluation of BO outcomes in urban areas.</p>