The world No. 7, who also won his match Friday, was the superior player following a tight opening set, winning 7-6 (3), 6-3, 6-3 at the Stade Pierre Mauroy in Lille. It's only the second time Croatia has been victorious in this event, with their previous success coming in 2005.
Croatia had taken a 2-0 lead after dominating Friday's matches, though France's hopes of glory were kept alive temporarily in the doubles Sunday.
Here's a recap of the result of each rubber from the final and a look back at Cilic's success Sunday.
(CRO) Borna Coric bt. (FRA) Jeremy Chardy 6-2, 7-5, 6-4
(CRO) Marin Cilic bt. (FRA) Jo Wilfried-Tsonga 6-3, 7-5, 6-4
(FRA) Pierre-Hugues Herbert & Nicolas Mahut bt. (CRO) Ivan Dodig & Mate Pavic 6-4, 6-4, 3-6, 7-6(3)
(CRO) Marin Cilic bt. (FRA) Lucas Pouille 7-6(3), 6-3, 6-3
It was confirmed ahead of this rubber that France skipper Yannick Noah was changing his lineup for the Sunday games, with Pouille stepping in for Chardy, who was beaten comfortably by Coric on Friday.
The match was a big chance for Pouille to finish a disappointing 2018 on a high, and the backing was evidently there for him to do so at a vociferous venue.
In the first set, he thrived off that support and didn't give Cilic much of an inch. The Frenchman conjured six aces and rarely looked trouble when he had the ball in hand, and even when the Croatian did apply pressure, Pouille was able to come up with some answers:
Still, in the tiebreak, Cilic never appeared to be flustered, and with the score locked at 3-3, he went through the gears, with four points in a row enough for him to secure the opening stanza.
For Pouille, it was always going to be a struggle from this point on, and early in the second set, there didn't appear to be the same spark in his play. Cilic capitalised on that, breaking to go 4-2 in front and eventually moving to within one set of the iconic silver bowl for his country.
You suspect there wouldn't have been any complacency in his play, though. Tennis journalist Gaspar Ribeiro Lanca noted that Cilic has been in a similar position before only to see things all go wrong:
There wasn't to be any drama for the Croatians this time, though, as a weary Pouille struggled to get into any sort of rhythm in the third set, and Cilic continued to play imperious tennis on serve.
A break to go 3-2 up was consolidated by the world No. 7, and he breezed through the rest of the match to clinch a historic triumph for Croatia.