Dadi was released by Perth Glory and was immediately picked up by the Phoenix in the January transfer window, the club seeing the big target man as a valuable addition to its current strikeforce.
The 36-year-old has arrived in Wellington and has already trained with his new teammates under coach Ricki Herbert.
Dadi played 22 Hyundai A-League games for Perth and scored 10 goals after joining the club for the 2008/09 season.
Phoenix chief executive Tony Pignata said the 1.88m, 81kg Dadi would provide another attacking option for the Phoenix, who already boast in-form strikers Paul Ifill and Chris Greenacre.
"Eugene's a vastly talented and experienced striker who will offer Ricki something different up front.
"He's a big, strong and cunning striker and as a club we feel he'll be valuable for us in the closing stages of the season as we seek to secure a spot in the playoffs."
An immensely popular figure with football fans off the field, Dadi is certain to attract a big following in Wellington.
"Eugene still has a fierce desire to achieve at the highest level and he's shown commitment and value to his previous clubs.
"We're certain that's exactly what he'll bring to the Phoenix."
Dadi will be available for selection for the Phoenix in their long-awaited return home to Westpac Stadium on Saturday to take on Brisbane Roar.
Another player licking his lips in anticipation of that clash will be Phoenix goalkeeper Liam Reddy, who bailed out from the Brisbane club late last year and signed with the Phoenix as an injury replacement for New Zealand World Cup hero Mark Paston.