Swiss Roger Federer will face seventh-seeded Marius Koppel in the final after defeating seventh seed Daniel Medvedev 6-1, 6-4.
Kopel, ranked 93rd in the world, beat second-seeded Alexander Zverev 6-3, 6-7, 6-4 in the other semi-final.
Medvedev pushed Federer into three groups when they met at the Shanghai Masters earlier this month but the Swiss did not face any similar risk today.
The 37-year-old saved a break point in the first half before his fervor subsided and the victory over his opponent was dealt a decisive blow to reach the final of Basel 14.
After losing the first set in a strange 20 minutes, Medvedev found himself retreating 5-1 in the second set but managed to frustrate Federer's chance to pick up a point to keep the match and keep it sent.
The Russian, who won the knockout in Tokyo, Wonston Salem and Sydney this season, broke Federer's lead without losing a point to keep his hopes of a comeback but the Swiss made it in the next half and finished the game in 65 minutes.
Federer, who won the ninth title of the tournament in his hometown, is the submerged Copil, who beat Croatia's sixth seed Marin Schilic last week.
