Ossari played for the youth club of Calcio Padova.
He made his debut in Serie A on 23 December 1995 in the last twenty minutes of the Piacenza-Padova over 1-1.
He took the field in the match against Napoli finished 4-2 for biancoscudati.
His career mostly alternated between Serie C1 and Serie C2 with the Novara, Giorgione, Cremonese (with which marks his only goal), Poggesi and Thiene.
On 1 July 1995 Ossari played for the National Under-18 team.