19-year-old Mbappe joined PSG on loan from Monaco in August with the option of a permanent move for £166 million in the summer and is widely regarded as the the future of world football. Jesus has scored 15 Premier League goals for Red Devil rivals Manchester City since arriving for £27 million from Palmeiras in January. The Brazilian is still only 20 years of age.
"I watched Gabriel Jesus play three years ago," Giggs said. "I watched Mbappe for a year. I was watching them with the scout and it was a no-brainer," the Welshman told 'The Times'.
The former Manchester United winger spent two years as assistant manager alongside ex-boss Louis van Gaal, and he admitted they clashed over the club's transfer policy.
"It was just like 'get them'. It would have been £5m or something - get them, loan them back - and that's where the recruitment could have been better," he added.
The Red Devils spent big under the Dutch manager, bringing in the likes of Angel Di Maria, Memphis Depay, Radamel Falcao, Morgan Schneiderlin and Anthony Martial, with only the latter still at Old Trafford.
"It was hard because Louis had his own ideas and you had to respect that, but, yes, we had a few arguments about a couple of them," Giggs concluded.