Tomic tops Karlovic in third-set tiebreaker to win Bogota
The 21-year-old Australian, who was born in Germany, won despite Karlovic firing 39 aces to 11 for Tomic.
The 29th-ranked Karlovic, 35, beat home favorite Alejandro Falla in last year's final and was seeking his first title of 2014. Tomic, ranked 124th, was playing his first ATP final since Sydney in January.
The third-seeded Australian pair Samuel Groth and Chris Guccione beat Nicolas Barrientos and Juan Sebastian Cabal of Colombia 7-6 (5), 6-7 (3), 11-9 to win the doubles title at Centro de Alto Rendimiento.