The transcription factors T-bet and Bcl-6 are required for the establishment of a T helper type 1 cell (T_H1 cell) and follicular helper T cell (T_FH cell) gene-expression profile, respectively. Here we found that high concentrations of interleukin 2 (IL-2) inhibited Bcl-6 expression in polarized T_H1 cells. Mechanistically, the low concentrations of Bcl-6 normally found in effector T_H1 cells did not repress its target genes because a T-bet–Bcl-6 complex masked the Bcl-6 DNA-binding domain. T_H1 cells increased their Bcl-6/T-bet ratio in response to limiting IL-2 conditions, which allowed excess Bcl-6 to repress its direct target Prdm1 (which encodes the transcriptional repressor Blimp-1). The Bcl-6-dependent repression of Blimp-1 effectively induced a partial T_FH profile because Blimp-1 directly repressed a subset of T_FH signature genes, including Cxcr5. Thus, IL-2-signaling regulates the Bcl-6–Blimp-1 axis in T_H1 cells to maintain flexibility with a T_FH cell–like gene profile.