Purpose <p>To examine the prognostic utility of the albumin-myosteatosis gauge (AMG) in patients diagnosed with locally advanced gastric cancer (LAGC) who underwent neoadjuvant chemotherapy (NAC) followed by radical gastrectomy.</p> Methods <p>Data from 198 patients who underwent NAC and radical resection of LAGC at our center between January 2014 and December 2021 were analyzed. The AMG was calculated as the product of skeletal muscle radiodensity and albumin levels. Logistic and Cox regression models were used to determine the predictive utility of pre- and post-NAC AMG for the pathological response and survival.</p> Results <p>A higher AMG, regardless of whether measured before or after NAC, was associated with better performance status and higher pathological response rates (<i>P</i> &lt; 0.05). In the multivariate analysis, pre-NAC AMG, rather than post-NAC AMG, was an independent predictor of the pathological response (odds ratio 2.621 [95% confidence interval {CI} 1.376–4.993]; <i>P</i> = 0.003). This predictive value was consistent across subgroups. Furthermore, post-NAC AMG, rather than pre-NAC AMG, was an independent prognostic factor for the overall survival (hazard ratio 0.611 [95% CI, 0.375–0.997]; <i>P</i> = 0.049) and recurrence-free survival (hazard ratio 0.538 [95% CI 0.338–0.857]; <i>P</i> = 0.009). This prognostic utility was consistent across most subgroups, except for the obese subgroup.</p> Conclusions <p>AMG may be a useful tool for predicting the response to NAC in patients diagnosed with LAGC.</p>