Consumer demands for healthier food have been growing over the last decades. Enriching conventional food with bioactive substances is one option to fulfill these demands. Solid lipid nanoparticles (SLN) are known as carrier systems for lipophilic bioactives. However, due to their large interface, they likely interact with the food matrix. We therefore studied how SLN affect the properties of cold set β-lactoglobulin (BLG) gels. BLG or Tween 20, typical excipients used for stabilizing SLN in suspensions, was applied to reduce or promote interactions between SLN and the protein matrix. Tween 20 stabilized SLN were incorporated before or after the heat treatment of the protein, BLG stabilized SLN were added after the heat treatment. Gels were analyzed regarding their mechanical properties, syneresis, and microstructure. All gels showed fine stranded network morphology. BLG stabilized SLN increased the Young's modulus of the gels with increasing particle content. They caused thick lamellae and ramifications within the gel. Their absence in the syneresis water confirmed that they acted as bound particles. Tween 20 stabilized SLN, incorporated before heat treatment, did not affect the Young's modulus. By contrast, Tween 20 stabilized SLN added after heat treatment decreased the Young's modulus and resulted in disrupted lamellae. Tween 20 stabilized SLN were washed out during syneresis to a certain extent. The results indicate the integration of BLG stabilized SLN in the network and their function as bound particles. SLN, stabilized by Tween 20, did not participate in the gel network and acted as unbound particles. Display omitted •Network structure, gel stiffness and syneresis can be influenced by incorporation of SLN into BLG-gels.•SLN filled gels become stiffer if SLN are stabilized by protein instead of Tween 20.•Impact of Tween 20-stabilized SLN on gel properties depends on time of incorporation.•Tween 20-stabilized SLN are unbound particles.