However, the 21-year-old believes that his route to the final played a part in his performance, while Ferrer's easier schedule helped the eventual champion.
"This was his fifth match; this was my eighth match. I was really tired. I was actually exhausted almost," said Janowicz.
"I'm only human, and I'm still happy about this final. David played today really good tennis. It was good enough to beat me today. He's a really experienced guy, he didn't get nervous.
"I've got a lot of confidence right now. I learned if you have big heart and you want to do something amazing and you're going to fight for this, you have a big chance to make it."
Janowicz became the first qualifier in almost a decade to make the final of the Paris Masters.