We developed a novel and rapid approach to access T celldependent 2:1 bispecific constructs by means of two subsequently performed IEDDA click reaction. Using our biogenic tyrosine SPOCQ-alkyne reaction, we first functionalized a genetically engineered therapeutic antibody with one TCO-handle, to which a tetrazine-functionalized bioactive molecule was clicked in a second step. Analysis of the isolated fractions revealed that the constructs are of decent purity (>71%), containing only inactive starting materials as byproducts. The generated bispecific constructs retained binding of both mAbs, activating the T cells to kill HER2 + HCC1954 cells, even at very low picomolar concentrations. With this additional approach to prepare 2:1 bispecific constructs, bispecific constructs can be generated with which T cell response is elicited using only one T cell-binding epitope.