The battle of the basin - the last round robin fixture in the top-six Central Otago competition - was won this time by Arrowtown with only one point the difference, 20-19, in a nail-biter at Jack Reid Park.
Arrowtown dominated at the start, with its blockbusting No 8 and player of the day Eddie Sefo dotting down for his first of three tries after 15 minutes.
Wakatipu then gained the ascendancy, and took a 13-7 lead after brilliant long-range tries by centre Danny King and winger Rob Lund. Arrowtown pegged that back to 13-10 with a penalty just before halftime.
Arrowtown got on top in the second half, Sefo scoring two more tries while Wakatipu captain and lock Dan Iosefo spent 10 minutes in the sin bin for a yellow card offence.
Wakatipu, down 20-13, added two penalties but, despite some promising moves, failed to breach Arrowtown's try-line.
Arrowtown coach Hayden Finch, who praised his forward pack and halfback Kelly Henderson, in particular, said he felt relieved at the finish.
''It's always great to beat Wakatipu. They've beaten us at home the last two times and we don't like that.''
Finch said he was surprised Wakatipu opted to kick a penalty while down 20-16, rather than going for a match-winning try.
''For some reason, they seem to be happy getting that one competition point to get a home semi.
''When we play Wakatipu, we always want to win.''
The focus for both teams is now the semifinals.
Arrowtown will travel to Ranfurly to take on Maniototo on Saturday and Wakatipu will host fourth-placed Cromwell, in Queenstown.
Kick-off for both games is 2.30pm.
- By James Beech and Philip Chandler.
