1988, Unión achieved the runner-up of the Copa Chile, after lossing against Colo-Colo. In 1989, the club disputed the Winter Cup, tournament designed by the ANFP, for keep active the club during the development of the Copa América 1989. In the contest, The Hispanics integrated the Group 3. Unión qualified to the quarter-finals. After winning the quarter-finals and the semi-finals, the club finally disputed the final against Huachipato, however, Unión won the game by 2–0, crowning champion of the contest. In 1992, arrived Nelson Acosta to the bench, former coach of O'Higgins. In the first season of Acosta in Unión, he proclaimed to Unión champion of the Copa Chile 1992, with Marcelo Vega as top-scorer of the team and the contest with 13 goals. However, the club was crowned for second consecutive time of the tournament in 1993, beating to Cobreloa by 3–1 at Estadio Nacional. In 1997, Unión Española completed a century of history. In this season, Unión was relegated for first time in its history to the Second Division, now called Primera B and the coach Acosta leave the club, because the relegation. For the season 1999, the directive hired to the coach Juvenal Olmos. 2000s Unión Española returned to the Primera División in 2000 with a then-record 70 points. In the Primera División, Unión finished in the fourth place. Because the departure of Juvenal Olmos to Universidad Católica, the former player Leonardo Véliz arrived as coach in 2001. The team was under the coach, Fernando Carvallo during two seasons (2003–04). In the second season of Carvallo in Unión, the club was eliminated in the quarter-finals of the play-offs by Santiago Wanderers, during the Torneo de Apertura, and in the Torneo de Clausura of the same year, Unión was runner-up of the tournament, after lossing the final against Cobreloa. Because the departure of the coach Fernando Carvallo to Palestino, he was replaced by Fernando Díaz Seguel, with Díaz Seguel as the coach, Unión Española was champion of the Torneo Apertura 2005, winning the sixth title in Primera División in its history. Because the title obtained in the Apertura 2005, Unión played the Copa Libertadores 2006. In this international tournament, Unión failed to qualify to the second stage. The club was ubicated in the third position with 8 points alongside Argentine club Newell's Old Boys, but Newells had more goal difference making that Unión was eliminated of the tournament.