Constantinidis currently heads the AMP director's office of financial planning advice and services.
"Amelia will bring considerable experience in advice policy and practice support to Horizons, enhancing its commitment to training the next generation of financial planners and supporting them to deliver quality financial advice," Helmich said.
The appointment comes as former director of Horizons, Tim Steele, moves into his new role as managing director of ipac. It forms part of AMP's review of the company's advice businesses.
Constantinidis' appointment completes the leadership team for the new AMP advice division headed by Steve Helmich and Andrew Waddell.