Janssen was on target for Fenerbahce on his debut for the Turkish club at the weekend.
The Netherlands international striker joined Fenerbahce on a season-long loan deal from Tottenham in the summer transfer window.
The 23-year-old scored after just 16 minutes against Alanyaspor from close range on Sunday to help his loan club win the away league fixture 4-1, as reported by The Daily Mail.
Tottenham manager Pochettino has expressed his delight at Janssen scoring for Fenerbahce on Sunday.
The Spurs boss has also explained why the club and Janssen decided that it would be better for the striker to leave the North London outfit on loan in the summer transfer window.
“I think it’s important for him because always all the players struggle in their first season in England,” Pochettino told Football.London about Janssen scoring.
“When you come from Netherlands it’s a different level of competition and in the end he wanted to leave and he decided to go to Turkey, and we wish him all the best and we are happy if he scored last night. It was really good for him, to try to build again his confidence.
“Here he sometimes played, sometimes didn’t play, but you know when you have Harry Kane in your position it’s not easy to fight and be motivated every day to try to give your best.
“It was his decision, with the club’s decision, to send him on loan but we hope he starts to build his confidence and trust and score goals.”
Janssen is a very promising and talented striker, and a spell away from Spurs on loan for the 2017-18 campaign will help him in the long run.