Cristiano Ronaldo's Portugal beat the Czech Republic 2-1 to claim a Euro 2024 debut victory on Tuesday but they needed to come from behind with a 92nd-minute winner from youngster Francisco Conceicao.
Earlier in the section's other clash, Turkey bested Georgia 3-1 in a pulsating match in Dortmund.
Roberto Martinez's Portugal qualified at a canter with a 100 percent record, but only just scraped victory in Leipzig in their first match, under driving rain.
Ronaldo played at a record-extending sixth European Championship and 41-year-old defender Pepe became the tournament's oldest ever player for the Selecao.
The Czechs went ahead against the run of play through Lukas Provod's fine strike from the edge of the box after the hour mark, but Robin Hranac's own goal soon pulled Portugal level before Conceicao's winner.
"We want to do more, but there was also a lot of emotion, a lot of desire and sometimes we failed to pull off the strategic plan," said Portugal midfielder Vitinha, awarded player of the match.
"We wanted to come out strong, show our strength and unfortunately we conceded the goal first, on the Czech Republic's first opportunity.
"We showed all our coolness and resilience."
Portugal supporters chanted Ronaldo's name and imitated his "Suuuui" celebration shout as they marched to the game waving flags and in high spirits despite a brief but intense thunderstorm.
Around 8,000 fans attended Portugal's open training session on Saturday, many of whom were just hoping for a glimpse of the 39-year-old former Real Madrid striker.
Thousands of fans sported replica Ronaldo shirts at the match but were unable to watch the all-time record Euros goalscorer find the net on a frustrating night against a solid Czech side.
Ronaldo was thrice denied by goalkeeper Jindrich Stanek on a record Euros appearance and headed against the post, but was offside.
Diogo Jota put the rebound into the net but the goal was disallowed after VAR highlighted Al Nassr striker Ronaldo's infringement.
It did not matter for Portugal in the end as 21-year-old Porto winger Conceicao, son of former Portugal international Sergio Conceicao, struck from close range.
"Francisco is the ultimate example of earning it, he deserves to be here and showed he is ready to help the group," Martinez told reporters.
The former Wigan and Everton coach defended his team's performance.
"Today we won, because the group is united, it's a very resilient group, we became resilient over the past few days," he said.
"(After conceding) it would have been very easy to blame each other but we didn't do that. We were a team."
The Czechs were left agonising after battling so hard and almost claiming a point.
"It hurts terribly when you work like this for 90 minutes, you give everything and you lose in the end," said Czech goalscorer Provod.
"Our defenders played an incredible game. We just needed a bit more luck."