The 26-year-old, struggling Bremen’s top scorer with nine goals this season, will sign a three-and-a-half year contract with an annual salary of around 50,000 euros per week.
He will link up with ex-Real Madrid coach and former Germany international Bernd Schuster at the big-spending Istanbul club.
Besiktas also boast Almeida’s fellow Portugal stars Simao and Ricardo Quaresma in their ranks, along with former Real Madrid midfielder Guti.
Almeida’s final act for Bremen in Germany was a hat-trick against St Pauli on November 28 - he was shown a straight red card late on and missed the last three Bundesliga games before the winter break.
