After winning the toss, the Dragons posted 276-6 in 50 overs.
Raynard van Tonder struck an unbeaten 129 off 145 balls, while receiving good support from Wihan Lubbe (46), Senuran Muthusamy (34) and Duan Jansen (33*).
Beuran Hendricks took 3-52 in 10 overs for WP, while Nandre Burger claimed two wickets.
After a rain delay, the visitors were set a revised target of 245 in 38 overs.
Verreynne hit 101 off 65 balls, before Edward Moore (41*) and Mpongwana (27*) got their team over the line with 3.5 overs to spare.
Migael Pretorius picked up 2-30 for the Dragons.
The match between the KZN Dolphins and Boland Rocks at Kingsmead in Durban was abandoned after only six overs due to rain, with the visitors on 32-0.
In Division 2, the Eastern Cape Iinyathi secured a five-wicket victory against the Eastern Storm in East London, the Northern Cape Heat defeated the Limpopo Impalas by 29 runs in Kimberley, while the Free State Knights secured a 12-run win against the Garden Route Badgers (SWD) in Oudtshoorn.
