Federer, who is debuting a new larger racquet, has struggled throughout the tournament and took three sets to beat home hope Florian Mayer in the quarter-finals.
However, Federer’s loss marks another defeat to a player outside the top 110 in the world following his surprise loss at the hands of Sergiy Stakhovsky at Wimbledon.
The Swiss, a four-time Hamburg winner, made a raft of unforced errors to offer the qualifier a route to his first career final.
For Delbonis, a final awaits against in-form Fabio Fognini, who beat third-seed Nicolas Almagro 6-4 7-6(1) in one hour and 50 minutes.
The win ensures a successive final appearance following on from last week’s win against Philipp Kohlschreiber at ATP Stuttgart - his first career title.
ATP Hamburg semi-final results
Federico Delbonis (Argentina) beat 1-Roger Federer (Switzerland) 7-6(7) 7-6(4)
12-Fabio Fognini (Italy) beat 3-Nicolas Almagro (Spain) 6-4 7-6(1)
ATP Bogota semi-final results
Alejandro Falla (Colombia) beat Vasek Pospisil (Canada) 6-7(4) 6-3 6-4
Ivo Karlovic (Croatia) beat 2-Kevin Anderson (South Africa) 6-4 6-7(4) 6-3
- Sports & Recreation
- Fabio Fognini
- Nicolas Almagro
- Florian Mayer