Background and Purpose FGF21 has emerged as a therapeutic strategy for treating type 2 diabetes mellitus due to its antidiabetic effects, and this has led to the development of long-acting analogues of FGF21. However, these compounds have some limitations, including a need to be administered by s.c. injection and their prolonged pharmacodynamic effect compared with native FGF21, which might be responsible for their reported side effects. Experimental Approach We have previously demonstrated that i.p. administration of haem-regulated eukaryotic translation initiation factor 2 alpha kinase (HRI) activators increases hepatic and circulating levels of FGF21. In this study, we examined the effects of p.o. administration of a new HRI activator, EPB-53, on high-fat diet (HFD)-induced glucose intolerance, hepatic steatosis, and hypertriglyceridaemia, and compared them with those of metformin. Key Results EPB-53 administration for the last 2 weeks, to mice fed a HFD for 10 weeks, reduced body weight gain, improved glucose intolerance, and prevented hepatic steatosis and hypertriglyceridaemia, whereas metformin only ameliorated glucose intolerance. Moreover, EPB-53, similar to the reported effects of FGF21, reduced lipogenesis in cultured human hepatocytes and in the liver of mice fed a HFD. Administration of EPB-53 to Fgf21-knockout mice had no effects, demonstrating that its efficacy is dependent on this hormone. Conclusions and Implications Overall, the findings of this study demonstrate that p.o. administration of HRI activators, by increasing FGF21, is a promising strategy for the treatment of type 2 diabetes mellitus and non-alcoholic fatty liver disease.