The 2008–09 Druga HNL (also known as 2. HNL) season was the 18th season of Croatia's second level football since its establishment in 1992. Croatia Sesvete were league champions and were promoted to Prva HNL at the end of the previous season.
The league featured 16 clubs, playing in a double round robin league system. The season started on 23 August 2008 and ended on 30 May 2009.
The following clubs have been promoted or relegated at the end of the 2007–08 season:
Promoted to 1. HNL
Relegated to 3. HNL
Relegated from 1. HNL
Promoted from 3. HNL
In a two-legged promotion/relegation playoff between Inter Zaprešić (as 11th placed 1. HNL team) and Hrvatski Dragovoljac (as 2. HNL runners-up), the former kept their Prva HNL status by beating Hrvatski Dragovoljac with 2–0 on aggregate (2–0, 0–0).
The top scorers in the 2008–09 Druga HNL season were:[3]