Introduction: Diets rich in refined carbohydrates are associated with cardiometabolic dysfunction, but the mechanisms linking metabolic disturbances to myocardial impairment in females remain unclear. This study investigated the effects of short-term consumption of a refined carbohydrate-rich diet on papillary muscle contractility in female rats. Methods: Adult female Wistar rats were assigned to either a control diet (CT) or a high-carbohydrate diet (HCD) for 15 days. The HCD consisted of 45% sweetened condensed milk, 10% refined sugar, and 45% standard chow. Metabolic, inflammatory, functional, and molecular parameters were evaluated. Myocardial contractility and intracellular Ca2+ handling were assessed in isolated left ventricular papillary muscles, while phospholamban (PLB), SERCA2a, and NCX1 protein expression were analyzed. Results: The HCD increased ovarian adipose tissue, triglyceride levels, glucose intolerance, and TNF-α levels, while decreasing HDL cholesterol and circulating adiponectin. Leptin and MCP-1 levels were unchanged. Functional assessments revealed impaired cardiac contractility, evidenced by reduced papillary muscle force and lower positive force derivative (dF/dt+). HCD also decreased post-pause potentiation and post-rest contraction, indicating impaired sarcoplasmic reticulum (SR) Ca2+ storage and release, as well as potentially reduced extracellular calcium influx. At the molecular level, PLB expression was increased, whereas SERCA2a and NCX1 expression remained unchanged. Conclusions: Short-term consumption of a refined carbohydrate-rich diet induces early cardiac contractile dysfunction in female rats, associated with impaired Ca2+ handling, reduced adiponectin, and increased inflammation, suggesting that metabolic and inflammatory disturbances precede structural cardiac alterations and may promote cardiometabolic disease development.