Between 1995 and 1997 he played for the Colorado Rockies. While the Rockies had high hopes for Swift, he struggled with a shoulder injury, back pains, and the psychological difficulties of the thin air of Colorado, and never again put up numbers comparable to his days with the Giants. He was eventually released by the Rockies due to shoulder trouble and triceps tightness.
In 1998, Swift returned to the Seattle Mariners. He struggled, posting an 11-9 record with a 5.85 ERA and 1.62 WHIP. After the season, he retired from baseball.
On December 22, 1999, USA Today named Bill Swift as one of Maine's best athletes of the 20th century.