Purpose Preclinical evidence suggests dichloroacetate (DCA) can reverse the Warburg effect and inhibit growth in cancer models. This phase 1 study was undertaken to assess the safety, recommended phase 2 dose (RP2D), and pharmacokinetic (PK) profile of oral DCA in patients with advanced solid tumors. Patients and Methods Twenty-four patients with advanced solid malignancies were enrolled using a standard 3 + 3 protocol at a starting dose of 6.25 mg/kg twice daily (BID). Treatment on 28 days cycles was continued until progression, toxicity, or consent withdrawal. PK samples were collected on days 1 and 15 of cycle 1, and day 1 of subsequent cycles. PET imaging (¹⁸ F-FDG uptake) was investigated as a potential biomarker of response. Results Twenty-three evaluable patients were treated with DCA at two doses: 6.25 mg/kg and 12.5 mg/kg BID (median of 2 cycles each). No DLTs occurred in the 6.25 mg/kg BID cohort so the dose was escalated. Three of seven patients had DLTs (fatigue, vomiting, diarrhea) at 12.5 mg/kg BID. Thirteen additional patients were treated at 6.25 mg/kg BID. Most toxicities were grade 1–2 with the most common being fatigue, neuropathy and nausea. No responses were observed and eight patients had stable disease. The DCA PK profile in cancer patients was consistent with previously published data. There was high variability in PK values and neuropathy among patients. Progressive increase in DCA trough levels and a trend towards decreased ¹⁸ F-FDG uptake with length of DCA therapy was observed. Conclusions The RP2D of oral DCA is 6.25 mg/kg BID. Toxicities will require careful monitoring in future trials.