The 24-year-old striker has signed a five-year contract at the Estadio da Luz.
The Mexico international failed to make an impact at Atletico Madrid since joining the club from America ahead of last season.
“I did not play the minutes I expected [at Atletico], but I believe in my worth and I want to show that I can help the team,” Jimenez said.
“I have the desire to play more to give the best of me. I know that it will not be easy. I’m in a great club and surrounded by high quality team-mates.
“I have a year of European football, and that has helped me to adapt. Now, with the help of everyone in this great club, I will work to make things better.
“I am delighted to be part of a club as important as this one. I really want to help so that Benfica continues with its success and I’m very hopeful of playing well.
“I want to train to win the confidence of the coach and my team-mates so I can get good performances on the pitch. I will do everything to help the team.”
Portuguese station SIC reports that a fee of €9m was agreed between the two clubs.
— Sport Lisboa Benfica (@SL_Benfica) August 13, 2015