Identification of components causing off-flavor requires experience and knowledge. The GC/MS Off-Flavor Analyzer includes a database containing parameters required for analysis and information (such as types and threshold values) about primary components that cause off-flavor. As a result, even less experienced analysts can use the system to easily start analyzing off-flavor components. This report introduces a case where we analyzed a packaged food product with a complaint about an off-flavor using a GC/MS Off-Flavor Analyzer. We were able to narrow down the substances that may have caused the off-flavor to four components by comparing the questionable product to the normal product. We also checked the off-flavor with a sniffer using sensory information contained in the GC/MS Off-Flavor Analyzer and successfully identified that the off-flavor was caused by anisoles. To ascertain the cause of the off-flavor, we separately measured each part of the product (package and food parts) and compared the concentration of anisoles. Results show that the package contained a higher concentration of anisoles, which caused the off-flavor. The system is expected to be used to identify the causes of off-flavors in foods, containers, and packages.