Croudis (Otago) claimed both the overall title, based on scoring average, and the two-round final played at Jack's Point and Millbrook last weekend.
He played 13 rounds on the tour and finished with a scoring average of -1.25, ahead of Thomas Facer (Otago), on 1.13, and Thomas Forbes (North Otago), on 2.88.
The tour included 10 events, with the best eight rounds counting for the order of merit.
Croudis (18) won the 36-hole final by shooting a polished 71 at Jack's Point and a 75 at Millbrook.
His two-round total of 146 was nine shots clear of Daniel O'Connor (Southland), with Forbes seven shots further back.
The tour, run by the Southern Golf Academy and established with funds from former professional Greg Turner, featured 14 boys from 10 Otago clubs and four from Southland clubs, as well as two Otago girls.
Croudis has had a remarkable season.
He won the New Zealand under-19 title at the North Shore club in September, then finished second in his age group at the Aaron Baddeley international event in China.
He missed out on a play-off at the New Zealand Open qualifying tournament by one shot, having to settle for an Open appearance as a caddy for Dunedin professional Mahal Pearce.
Croudis was awarded the Sir Bob Charles Scholarship to assist with both his golf development and studies at the University of Otago.
