The 35-year-old Gomez, a 15-year NHL veteran, attended training camp on a professional tryout. He had seven goals and 27 assists in 58 games last season for New Jersey.
St. Louis added forward Scottie Upshall on Monday, also after a tryout.
The Blues placed forward Patrik Berglund on long-term injured reserve. Berglund underwent shoulder surgery in August and will be evaluated in four months.