trans-Resveratrol, a natural polyphenol present in grapes, has many beneficial effects to human health. However, measurement of trans-resveratrol is technically complicated and time-consuming. In the present study, we obtained a sensitive and specific monoclonal antibody (mAb), namely 3C9, against trans-resveratrol. An indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed, with 50% inhibitory concentration and working range of 1.0 ng/mL and 0.19-4.9 ng/mL, respectively. A lateral flow immunoassay (LFIA) based on 3C9 was also developed for the semiquantitative detection of trans-resveratrol in an indicator range of 50-100 ng/mL. Average recoveries of trans-resveratrol spiked in red and green grape berries samples were respectively 88-107% and 83-102% by icELISA. The icELISA and LFIA were applied for determination of trans-resveratrol in grape berries. The results were highly consistent with those determined by high-performance liquid chromatography analysis (R2 = 0.9997). Therefore, we conclude that the immunoassay methods are suitable for the large-scale screening of trans-resveratrol in grape quality breeding.