The 20-year-old Australian recently spent time with Dutch club FC Eindhoven, where he made eight appearances in the Eerste Divisie and will arrive in Wellington this week in search of first-team football.
Phoenix general manager David Dome said the Wellingtonians still hadn't written off the season, which has included outspoken owners, tactical changes and calls for coach Ricki Herbert to walk given the side's poor form.
"We haven't given up on the finals. We certainly believe that we've got the players on board to get us there," Dome said.
"We know they've done the job in the past and we just need a little bit of an edge and a little bit of a kickstart and Corey is hopefully going to be that type of player that we can build around for a little late surge in to the finals and that fifth and sixth position. We've got a couple of games coming up with teams in and around those positions that are really, really important."
The Phoenix travel away to Brisbane this Sunday to meet a Roar side who have been a shadow of their former selves, but Wellington's woeful record at Suncorp Stadium doesn't inspire confidence.
Following that they host Adelaide and Newcastle, which both loom as games that the Phoenix should win if they are a playoff-calibre team.
The Phoenix then meet the Melbourne Heart in a home-away-from-home game in Dunedin on March 3, then travel to Parramatta to meet the third-placed Western Sydney Wanderers, followed by a trip to Perth, before rounding out the campaign against the high-flying Melbourne Victory at Westpac Stadium on March March 31.
Gameiro's acquisition is curious in the sense that Wellington trumpeted the signing of former Belgian international Stein Huysegems at the beginning of the season but after a promising start the 30-year-old hasn't scored since October.
He started five of the past six games but hasn't looked in tune with his midfielders, while Jeremy Brockie has been industrious up front and has bagged 11 goals this season.
The Phoenix will seek an international clearance for Gameiro tomorrow (mon) but he looks a good bet to be included in the squad for the trip to Brisbane given he will come to Wellington without any fitness concerns.