Poki (22) will join the squad as cover for injured backs Kurt Baker and James Paterson and will be with the team at least until March.
Poki had been in the Crusaders for the past two seasons but was hampered by a hamstring strain last season and did not get a lot of playing time.
He is an exciting acquisition for the Highlanders and looked good in the limited opportunities he got in an under-performing Tasman team in the ITM Cup.
Baker has a back injury and has been ordered to rest. He will have a further assessment next month but looks a doubtful starter for the Super 15.
Paterson had an injury-riddled debut season for Southland and broke his leg in one of the final matches of the season.
Although Paterson is expected to be back for the start of the season, Poki helps the squad in giving the side more options as he can play centre and wing.
The squad will formally get together on December 13 to start training, and will then disband for a Christmas break on December 23.
It will resume training on January 10.
With most players having had up to seven weeks off since their last game, the squad should not be lacking motivation to get out and train.
Highlanders general manager Roger Clark said the collective agreement between the New Zealand Rugby Union and the New Zealand Rugby Players Association stipulated the periods of rest and time off for players.
He said no matter how long the players did or did not get off, the team just had to get on with the job.
"Whether we have got four weeks, six weeks, or even two weeks together, it is what it is and we just have to knuckle down and get on with it," Clark said.
Some Australian teams have been training for weeks but Clark said those sides did not have to contend with a domestic competition, and there was always the hazard of training for too long.
The team would have a four-day camp in Wanaka in January and next week a few senior players, along with coaching and management staff, would journey to Stewart Island for a couple of days to discuss the coming season.
"It's about setting the scene for the season, looking at what we want to do and how we are going to move forward."
All Blacks Jimmy Cowan and Tom Donnelly are expected to join the team in mid-January.
A new strength and conditioning coach, Andrew Beardmore, has been appointed. He previously worked with the Hurricanes. Chris Lapage, who previously worked with Wellington, is the new video analyst and Craig McColl is the new physiotherapist.
New scrum coach Steve Cumberland is not expected to join the team until February or March, depending on how the Japanese side he coaches, Kobe Steel, fares in the Japanese championship.
The Highlanders start their season with a game against the Hurricanes on February 18 in Wellington. They have pre-season games against the Blues, in Balclutha on January 29, the Chiefs, in Taupo on February 5 and the Crusaders, in Oamaru on February 11.
