HNL) was the 23rd season of Croatia's second level football competition since its establishment in 1992.
NK Zagreb were league champions and earned a place in Croatia's first division, Prva HNL.
Only two teams from Treća HNL were granted license for competing in the Druga HNL, HNK Segesta and HNK Val.
Segesta won the qualification playoffs by 3-2 on aggregate and earned a place in Druga HNL.
Zagreb, Cibalia and Inter Zaprešić were relegated from 2012–13 Prva HNL.