Background/Objectives: Numerous studies have documented cardioprotective effects of adiponectin in animal models of cardiometabolic disease (CMD). Adiponectin receptor agonist ALY688 has demonstrated functional significance against pressure overload-induced cardiac remodeling events in a mouse model of heart failure with reduced ejection fraction (HFrEF), potentially through modulation of the systemic metabolome. However, the specific metabolites and their pathophysiological contribution to cardioprotection in cardiac hypertrophy or heart failure remain unclear. This study aimed to characterize systemic metabolic alterations across five tissues in HFrEF and determine how ALY688 modifies these pathways to mediate cardioprotection in the transverse aortic constriction (TAC) model. Methods: Targeted metabolic profiling was performed on heart, liver, muscle, epididymal white adipose tissue (eWAT), and serum collected five weeks post-surgery from wild-type male C57BL/6 mice. Mice underwent either Sham or TAC-induced left ventricular pressure overload, with or without daily subcutaneous ALY688 administration. Metabolites were quantified using liquid chromatography–tandem mass spectrometry (LC–MS/MS) and statistically analyzed at the tissue level. Results: Consistent with pathological cardiac remodeling, the comprehensive metabolomic analysis revealed that TAC induced widespread disruption of systemic metabolic homeostasis. ALY688 treatment significantly modified several key metabolite classes, including triglycerides (TGs) and glycosylceramides (HexCer). Notably, ALY688 also altered multiple gut-derived metabolites, including trimethylamine N-oxide (TMAO), 5-aminovaleric acid (5-AVA), and glycodeoxycholic acid (GDCA), highlighting a potential gut–liver–heart axis mediating its cardioprotective effects. Conclusions: These findings demonstrate that ALY688 mitigates TAC-induced metabolic dysregulation across multiple tissues. The identified metabolic signatures suggest that ALY688 exerts cardioprotective effects, at least in part, through restoration of systemic metabolic homeostasis and engagement of a gut–liver–heart metabolic axis. These results provide mechanistic insight into adiponectin receptor agonism and support further exploration of ALY688 as a potential therapeutic strategy for HFrEF.