Agostini started his professional playing career with Cesena in 1982. In 1986, he signed for A.S. Roma, scoring a total of six goals in forty appearances throughout two seasons. He then returned to Cesena before joining A.C. Milan in 1990, where he was rarely featured in the starting lineup and played only 12 matches, scoring two goals, as Milan won the European Super Cup and the Intercontinental Cup in 1990. He then played for Parma, Ancona (two seasons, the first in Serie A and the second in Serie B). With Parma, he won the 1991–92 Coppa Italia, and with Ancona, he was the top scorer during the 1993–94 Serie B, scoring 18 goals. He then moved to Napoli for two seasons, scoring 13 goals, before returning to Cesena in 1996. In 1999, he finally left Cesena, joining Ravenna, and spent successive seasons with minor league teams such as Spezia, Tivoli, Forlì and Cesenatico.