The disclosure provides fusion proteins specific for both CD137 and PD-L1, which fusion protein can be used to co-stimulate lymphocyte activation in a PD-L1-target-dependent manner. Such fusion proteins can be used in many pharmaceutical applications, for example, as anti-cancer agents and/or immune modulators for the treatment or prevention of human diseases such as a variety of tumors. The present disclosure also concerns methods of making the fusion proteins described herein as well as compositions comprising such fusion proteins. The present disclosure further relates to nucleic acid molecules encoding such fusion proteins and to methods for generation of such fusion proteins and nucleic acid molecules. In addition, the application discloses therapeutic and/or diagnostic uses of such fusion proteins as well as compositions comprising one or more of such fusion proteins.