The 1998 Cal Poly Mustangs football team represented California Polytechnic State University during the 1998 NCAA Division I-AA football season. Cal Poly competed as an NCAA Division I-AA independent in 1998. The Mustangs were led by second-year head coach Larry Welsh and played home games at Mustang Stadium in San Luis Obispo, California. In a big drop-off from their 10 win season in 1997, the 1998 Mustangs finished the season with a record of three wins and eight losses (3–8). Overall, the team was outscored by its opponents 226–299 for the season.