Background: Little is known about the nutritional care provided to patients who develop hospital acquired malnutrition (HAM). The present study aimed to describe the quality of nutritional care provided to patients who developed HAM and determine whether this differed by length of stay (LOS). Methods: A retrospective medical records audit was conducted on adults with LOS > 14 days across five Australian public hospitals from July 2015 to January 2019 who were clinically assessed to have HAM. Descriptors and nutrition-related care data were sourced. Descriptive statistics were conducted. Chi-squared and t-tests were used to compare patient data by LOS ≤ or > 50 days. Results: Eligible patients (n = 208) were 64% male, with median (range) LOS of 51 (15–354) days, body mass index = 26.8 ± 6.2 kg m−2 and mean ± SD age of 65 ± 17 years. Malnutrition screening was first completed a median (range) of 0 (0–31) days after admission, with weekly screening conducted on 29% of patients. Mean (range) time to initial dietitian assessment was 9 (0–87) days and 27 (2–173) days until malnutrition diagnosis. Thirty-seven percent of patients were weighed within 24 h of a dietitian requesting it, and 51% had fluid retention that may have masked further weight loss. Most (91%) patients consumed < 80% of nutrition requirements for > 2 weeks. However, 54% did not receive additional nutrition support (e.g., enteral nutrition), which was not considered by the dietitian in 28% (n = 31/112) of these patients. Only 40% consumed adequate intake prior to discharge. Those with LOS > 50 days (50%, n = 104/208) took 24 days longer to be diagnosed with malnutrition and lost 2.4 kg more body weight during admission (p < 0.010). Conclusions: Opportunities exist to optimise nutritional care to facilitate the prevention and management of hospital acquired malnutrition in long-stay patients.