Aims Malnutrition is highly prevalent in patients undergoing major head and neck (HN) surgery and is associated with adverse postoperative outcomes. A combined prehabilitation and ERAS protocol (ERAS+) aims to improve surgical resilience and recovery, but little is known regarding nutrition outcomes. Our primary aim was to determine whether ERAS+ reduced malnutrition rates in major HN surgery patients, diagnosed via the Patient Generated Subjective Global Assessment (PG-SGA). Secondary aims assessed (1) impact on nutrition parameters such as oral intake commencement and NGT removal, and (2) discriminative validity of the Malnutrition Screening Tool (MST) against PG-SGA. Methodology A multidisciplinary ERAS+ program was implemented in consecutive patients undergoing major HN surgery with free flap (FF) reconstruction (excluding scalp) between January 2022-August 2024 at a tertiary hospital. Nutrition outcomes were collected prospectively and analysed retrospectively, comparing ERAS+ patients (May 2023-August 2024) with pre-ERAS+ cohort (January 2022-January 2023). Results In 172 patients (pre-ERAS+ n=76, ERAS+ n=96), ERAS+ was associated with less deterioration in acute admission PG-SGA score (median Δ = 2 vs 5; p = 0.308), improved post-operative (day 1) energy (p=0.003) and protein intake (p=0.001), reduced NGT duration (3 days; p=0.003), and earlier free fluid initiation (1 day; p<0.001), and diet commencement (2 days; p=0.004). The MST demonstrated high specificity (92.7%) but poor sensitivity (31.8%), failing to identify risk in 68.2% of patients who were malnourished by PG-SGA on initial presentation. Conclusion Improvements in early postoperative nutritional recovery and adequacy were observed with implementation of an ERAS+ program in patients undergoing HN surgery with FF reconstruction. The inability of the MST to detect malnutrition risk in 68.2% of malnourished patients reinforces the importance of early dietetic assessment and intervention in this cohort.