Paire beat Pablo Carreno Busta 7-5, 6-1, 6-0 on the indoor hard court at Stade Pierre Mauroy before France's No. 1 player Pouille defeated Roberto Bautista Agut 3-6, 7-6 (5), 6-4, 2-6, 6-4.
"It's well deserved," France captain Yannick Noah said. "Benoit wore out Carreno Busta then we saw a crazy match, with a lot of unexpected developments, Lucas was fantastic."
Spain is without top-ranked Rafael Nadal, who was ruled out because of the right knee injury that forced him to retire from his U.S. Open semifinal against Juan Martin del Potro last week.
Pouille and Bautista Agut fought for 3 hours, 41 minutes in the northern city of Lille. The Frenchman was erratic at times and sharp at the end. He had 52 winners and 87 unforced errors but played the more aggressive tennis in the decider, serving extremely well on important points.
Pouille, who won the decisive fifth match in the 2017 final, saved a break point in the final game of the fifth set with a winning serve, then earned his third match point with an ace and sealed his win when Bautista Agut sent a forehand wide.
In the doubles on Saturday, Julien Benneteau and Nicolas Mahut are set to face Marcel Granollers and Feliciano Lopez.
Croatia leads the United States 2-0 in the other semifinal in Zadar, Croatia.
Carreno Busta started well against Paire but was hampered by a left thigh injury he picked up during the match and did not chase his opponent's shots in the final set.
Paire looked submerged by emotions when France's national anthem was played during the teams' presentation ceremony and was very tense in the opening set, hitting nine double faults.
Carreno Busta broke for 3-2 but dropped his serve in the 10th game when Paire hit a fine crosscourt forehand winner. Paire held his serve then produced aggressive returns and converted his first set point with a drop-shot volley.
Carreno Busta was completely unsettled and started to make too many unforced errors in the second set as Paire jumped to 5-0. Carreno Busta finally stopped a nine-game losing streak before Paire served out the set with an ace.
The 21st-ranked Spaniard asked for a medical timeout to receive treatment on his left thigh and returned to the court heavily bandaged. Things did not improve for the former U.S. Open semifinalist, who looked hampered in his moves and quickly gave up the fight.
"It was normal to be emotional at the start, I had warned the captain it would be difficult for me," said Pouille, who lobbied Noah this summer to get his first selection two years after being sent home from the Rio de Janeiro Olympics.
The hot-tempered Paire was excluded from the Rio Games after the French Tennis Federation accused him of breaking team rules.
"This episode at the Olympic Games has left a mark on me," Paire said. "It's terrific to be surrounded by all these people, I'm glad Yannick trusted me."
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