The former Gunners captain was a second-half substitute as the sides drew 2-2 in the first leg of their Champions League quarter-final.
Henry scored a record 226 goals in 369 games over eight seasons with Arsenal before leaving for Barca in 2007.
Fans' favourite: Henry and the Arsenal supporters have a special relationship
He was cheered on to the pitch and received a standing ovation at the end of the match.
The 32-year-old Frenchman said: 'It was very emotional. It was very special. Obviously coming on I got a good reception but the special moment was at the end.
'I said to myself I had to clap the Arsenal fans for the welcome back and you saw what happened after that.
'Obviously I have never hidden my love for the club and I think the fans showed there was still love for me. It was amazing.'
The Catalan giants looked as if they would blow their hosts away and led 2-0 after Zlatan Ibrahimovic's double. But Theo Walcott and Cesc Fabregas levelled the scores and Henry added: 'I'm not surprised they came back, especially with the fans. It always helps.
'You can be 2-0 down and if the fans start to boo it is hard but they were helping them to come back in the game. I know exactly what can happen here.
'It would have been better if we had won but 2-2 is not a bad result.'
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