His professional career began with his hometown club, Udinese, making his debut in a 0–0 draw against Napoli on 23 March 1980.

[2] After his time with Juventus, Luigi moved to Inter Milan for a year, then transferred to Reggiana in 1993, ending his professional career after two seasons with the club.

He also took part in Italy's footballing campaign at the 1988 Summer Olympics, where they managed a fourth-place finish after reaching the semi-finals yet again.

He was also a substitute member of Italy's squad at the 1990 World Cup on home soil, where the team also managed to reach the semi-finals, only to suffer a penalty-shootout defeat to defending champions Argentina, following a 1–1 draw after extra-time; despite the loss, De Agostini was able to net his penalty in the shoot-out.

[2] Unfortunately, his time with Juventus also included his last game for the Italy national team on 25 September 1991 in a 2–1 home loss to Bulgaria.

[2][6][7] De Agostini was a tactically versatile and hard-working defender, who could play on the left, or even in the centre of his team's defensive line, although he was capable of playing anywhere along the left side of the pitch, due to his ability to cover the flank effectively and assist his team both offensively and defensively.

He started out as a forward, but he was primarily deployed in the role of an attacking left-back or wing-back throughout his career, due to his pace, stamina, marking, crossing, positional sense, technical ability, and his capacity to read the game.