In early clinical trials the anticancer ruthenium complex KP1019 (trans-[tetrachlorobis(1H-indazole)ruthenate(III)]) stabilized disease in five of six evaluable patients and displayed no dose-limiting toxicity, suggesting that this drug may be a viable alternative to platinum-based chemotherapeutics. Although KP1019 has been shown to damage DNA in both cancer cell lines and the budding yeast Saccharomyces cerevisiae, this ruthenium complex’s mechanism of action remains unclear. Alternative explanations for KP1019’s toxicity stem from the drug’s ability to induce oxidative stress and to bind to diverse small molecules and proteins within cancer cells. Here we use an unbiased proteomic approach to characterize S. cerevisiae’s response to KP1019. Bioinformatic analysis of induced proteins confirmed that KP1019 activates DNA damage and oxidative stress response pathways. Clustering and analysis of both induced and repressed proteins revealed complementary metabolic retooling. Observed changes in protein expression suggest increased synthesis of methionine and the antioxidant glutathione. Moreover, yeast treated with KP1019 increased expression of evolutionarily conserved enzymes of the pentose phosphate pathway (PPP), including the glucose-6-phosphate dehydrogenase Zwf1, the 6-phosphogluconolactonase Sol4, and the transketolase Tkl2. KP1019-dependent induction of the rate-limiting PPP enzyme Zwf1 was verified by flow cytometry of Zwf1-GFP yeast treated with varying concentrations of the drug. Culturing yeast in media containing the PPP substrate xylose both induced Zwf1-GFP and increased resistance to KP1019, suggesting that upregulation of the PPP contributes to drug tolerance. This conclusion was further supported by KP1019-dependent repression of the PPP regulator Pho13. Deletion of the phosphatase-encoding gene PHO13 has previously been shown to upregulate the PPP, and here we show that pho13Δ yeast are more resistant to KP1019 than an isogenic wild-type control. Since glutathione and the PPP have well-established roles in cellular adaptation to oxidative stress, these data suggest that oxidative stress contributes to KP1019 toxicity and that metabolic re-tooling is an important contributor to cellular tolerance of this drug. Ultimately, metabolic biomarkers may prove suitable for use in predicting patient responses to this promising chemotherapeutic.