One person was in each vehicle and both needed to be extricated from them following the crash, a Fire and Emergency New Zealand spokesman said.
The NZ Transport Agency reports SH1 is closed between Beaconsfield Rd and Pareora River Rd following the crash.
A detour is in place, southbound traffic is asked to use Beaconsfield Rd, left on to Holme Station Rd, left on to Pareora River Rd and right back on to SH1. Reverse for those travelling northbound.