The 23-year-old Germany international revealed he considered a PSG transfer in January, but was told to stay by Dortmund.
Tuchel – who is desperate to bolster his squad after PSG won Ligue 1 but fell short in the Champions League – was asked about Weigl at the French Open on Tuesday.
Speaking to Eurosport Germany with Boris Becker, Tuchel said: "Of course [we're interested]. Julian is always an interesting player."
Weigl – who arrived from 1860 Munich in 2015 – made 18 Bundesliga appearances and scored one goal as Dortmund finished runners-up to Bayern Munich.
PSG sensation Kylian Mbappe was also a topic of conversation for Tuchel amid question marks over the World Cup-winning forward.
Mbappe – a reported target for Real Madrid – hinted he could be tempted by a "new project", while Tuchel has refused to offer guarantees over his future.
The 20-year-old scored a Ligue 1-high 33 goals as PSG retained their crown, and 39 in all competitions.
"Kylian has an unshakable confidence in him. I never saw that," Tuchel said. "It could be mistaken for arrogance, but for him, it's total confidence, which is normal when you know he wants to become the best player in the world."