Tangeretin, a polymethoxyflavone found in citrus peel, has been shown to have antiatherogenic, anti-inflammatory, and anticarcinogenic properties. However, the underlying target pathways are not fully characterized. We investigated the tangeretin sensitivity of yeast (Saccharomyces cerevisiae) mutants for DNA damage response or repair pathways. We found that tangeretin treatment significantly reduced (p < 0.05) survival rate, induced preferential G1 phase accumulation, and elevated the DNA double-strand break (DSB) signal gamma H2A in DNA repair-defective sgs1 Delta cells, but had no obvious effects on wild-type cells or mutants of the DNA damage checkpoint (including tel1 Delta, sml1 Delta mec1 Delta, sml1 Delta mec1 Delta tel1 Delta, and rad9 Delta mutants). Additionally, microarray data indicated that tangeretin treatment up-regulates genes involved in nutritional processing and down-regulates genes related to RNA processing in sgs1 Delta mutants. These results suggest tangeretin may sensitize SGS1-deficient cells by increasing a marker of DNA damage and by inducing G1 arrest and possibly metabolic stress. Thus, tangeretin may be suitable for chemosensitization of cancer cells lacking DSB-repair ability.