The England-born 22-year-old spent three years in the development academy at Saracens, before moving to New Zealand aged 18 to fulfil his ambitions of playing top-flight rugby.
Edinburgh head coach Michael Bradley said: "We're very pleased to secure the services of Piers Francis, as his introduction will strengthen and increase the competitiveness of our squad across a number of positions."
He added: "He's a very talented individual who is quick, skilful and has a fantastic eye for breaking the line. He's a very good fit for Edinburgh Rugby."
With the 2012 southern hemisphere season now at an end, Francis arrives in Scotland on Wednesday and will begin full training immediately.
He said: "Coming from the UK, I was very excited by an approach from Edinburgh Rugby and it moved very quickly from there.
"It's a new challenge in two great competitions (RaboDirect PRO12 and Heineken Cup), where I can test myself and integrate some of the southern hemisphere ways in my game into a club that's packed with internationals.
"I believe I have the skills and the attitude to enjoy success with Edinburgh Rugby and see this as another great opportunity for me to develop my game even further as part of a very professional set-up alongside great players and great coaches."