The Brazil worldwide has signed a deal until 2023 at Spurs after being told he could find a new club, while sources close to PSG told ESPN FC that a late delay came from final negotiations over the €28m fee plus a potential additional €4m in bonuses.
Spurs landed the jet-heeled Brazilian winger from Paris Saint-Germain on transfer deadline day for around £25m.
That is because Moura hadn't played a single minute of PSG's Champions League campaign in the first half of the season.
It's also been announced that Lucas, who has 36 global caps to his name, will wear the No. 27 shirt.
PSG splashed out £38 million to sign Moura from Brazilian club Sao Paolo and he was at the time considered as being one of the best up and coming talents in South America.
Pochettino continued: 'If not, then they need to compete.
Lucas Moura is unlikely to make his Tottenham debut against Liverpool this Sunday due to a lack of match fitness. Yes, it's very painful but I think Juan, when we signed him, we believed him to be a future, potential top player and of course he's going to play now. Since taking charge at White Hart Lane in 2014, he has gradually built Spurs into a side that now expects rather than hopes for Champions League football.
"Now we have time to think about the final, we will prepare better for the final than last season", he added, after seeing his side thrashed 4-1 by PSG a year ago.
Moura has been capped 34 times for Brazil and won the 2013 Confederations Cup and a silver medal at the London Olympics in 2012.