Ryan Draper, 27, from Caerwys, died and his girlfriend is critical but stable in hospital in Stoke.
The incident at 00:46 BST on Saturday on the B5122 at Caerwys involved a Vauxhall combo van.
The driver, a 42-year-old man, has since been released on bail.
Mr Draper's family said in a statement: "Both Hilary and David Draper, and his brother Joshua are deeply saddened at the loss of our loving son Ryan who was tragically and suddenly taken from us.
"We loved him so much and he will always be in our hearts. God bless him and we pray that his girlfriend makes a full recovery."
Sgt Jason Diamond, from North Wales Police' Roads Policing Unit, said: "We continue to appeal for witnesses, in particular to anybody who may have seen two pedestrians walking along the B5122 in Caerwys to come forward.
"Our investigation is ongoing and the family of Mr Draper are being supported by a specially-trained Family Liaison Officer."
A van driver has been arrested on suspicion of causing death and serious injury by dangerous driving after one pedestrian was killed and another was left seriously injured, in Flintshire.