This study is focused on the aggregation behaviour of kraft lignin (KL) in presence of different types of surfactants at elevated temperatures. Especially the initial part of the aggregation process, the nucleation and onset, is of interest. KL aggregation is induced either by adding surfactants or salt. The KL-surfactant interactions are found to be different depending on the type of surfactant. Starting with KL as a negatively charged polymeric fragment and adding a positively charged surfactant, the aggregation behaviour is significantly influenced. However, adding non-ionic surfactants without obvious head group interactions to the KL solutions, or surfactants with negatively charged head groups, completely different aggregation processes and particle structures are observed.