The 31-year-old has previously played for Chicago Griffins, Cornish Pirates and Taranaki.
Tongan international Willie Helu has also sealed a move to Adams Park after the deal was delayed due to injury.
"We've unfortunately been hit by a few early season injuries to our back line so having Andrew and William come in this week has been good timing," Sky Sports News quotes director of rugby Dai Young as saying.
"They are both experienced international players and provide us with vital depth in the midfield and wider."
Wasps are currently in ninth place in the Aviva Premiership table.