The 23-year old defender has returned home to New Zealand by signing a two-year deal with the Phoenix and exciting head coach Ricki Herbert who feels he has strengthened his defensive stocks.
"Michael is a big, strong, quick defender who has impressed me when I've had him in All Whites squads," Herbert said.
"He has been playing in a good league and I'm confident he will be quickly up to speed with the A-League."
Boxall added: "I've heard what a close-knit squad the club has, and I already know a handful of the lads through the All Whites, so I'm sure I will quickly settle down there.
"New Zealand has come a long way on the professional football front thanks to the Phoenix and I'm grateful to get the chance to play for Ricki and the club."