The tennis ace beat Del Potro 6-7, 6-4, 6-3 to seal his eighth title at the event.
Federer momentarily lost his cool during the clash, smashing his racket on the net before regaining his composure see off the Argentinian.
The Swiss star was twice a ball boy at the tournament, and has made it a tradition to splash out on takeaway for the youngsters when he is successful.
The 36-year-old looked close to tears after clinching victory, but quickly put on a brave face and was all smiles when lifting the trophy.
Scroll through the gallery above to see the best pictures of an emotional Roger Federer after winning the Swiss Indoors.