T cell activation is a multi-step process that results in proliferation and cytokine secretion to direct protective and pathological immune responses. The activation process is highly coordinated and requires the integration of signals from antigen recognition via the T cell receptor (TCR), costimulatory molecules, and cytokines. This chapter outlines methods to induce T helper cell (Th cell) activation in vitro and assesses its functional outcomes, including cytokine transcription and production, expression of surface activation markers, and proliferation. Two primary activation protocols are described: antigen-specific activation by the cognate antigen and presenting cells, and antigen-non-specific stimulation via anti-CD3/CD28 antibodies. The former emulates physiological conditions, while the latter offers reproducibility. We will then describe protocols for quantifying transcriptional and protein-level responses upon T cell activation.