Bulk ^{13}C polarization can be strongly enhanced in diamond at room temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating single crystals at a ∼50 mT field promoting anticrossings between electronic excited-state levels, followed by shuttling of the sample into an NMR setup and by subsequent ^{13}C detection. A nuclear polarization of ∼0.5%-equivalent to the ^{13}C polarization achievable by thermal polarization at room temperature at fields of ∼2000 T-was measured, and its bulk nature determined based on line shape and relaxation measurements. Positive and negative enhanced polarizations were obtained, with a generally complex but predictable dependence on the magnetic field during optical pumping. Owing to its simplicity, this ^{13}C room temperature polarizing strategy provides a promising new addition to existing nuclear hyperpolarization techniques.