The 30-year-old, who has returned to his native Northland after just one season with Leinster, amassed a total of 282 points (5 tries, 49 penalties and 55 conversions) in 22 appearances in blue.
Twice voted Leinster's player of the month, Holwell, who represented New Zealand 'A' in 1998 and 2000, was always favoured for the award.
Other winners at the ceremony, held at Dublin's Burlington hotel on Saturday night, included Greystones back row Rob Connolly (Leinster Senior Club Player of the Year), whose try-scoring heroics - 18 in 18 league games - helped the Wicklow men to their second AIB League Division Three play-off final win in two seasons.
Retired number 8 Victor Costello was the recipient of a special merit presentation for his outstanding contribution to Leinster Rugby over his 10-year representative career.
Other award winners included: Leinster League Player of the Year - Joey Moran (Naas RFC); Leinster Womens Player of the Year - Orla Brennan (Navan RFC); Leinster Young Player of the Year - Jamie Heaslip (Dublin University FC); Leinster Volunteer of the Year - Harry Brooks (Clontarf FC)