Both countries are holding pre-tournament training camps in Durban and the teams decided it would benefit both to hold joint training sessions from Monday to Wednesday.
"It will be great preparation for us to train with a team that is also going to the World Cup," said Springbok coach Heyneke Meyer.
"Namibia have done well recently, successfully defending their African Cup title and showing a massive improvement from last year.
"I'm excited to be working with them - they have a core of experienced players and management we know well and I'm sure we'll be able to tap into each other's expertise as we get ready for the World Cup."
"The training camp in Durban is vital for our preparations as it will expose our players to tier one opposition," added Namibia coach Phil Davies.
"The focus will be on delivering our systems efficiently under pressure and we are hoping for confirmation that our structures in attack and defence work against a world-class team.
"It is a great opportunity for us to replicate a World Cup week."
Namibia is in a pool with New Zealand, Argentina, Georgia and Tonga while the Springboks are pooled with Japan, Samoa, Scotland and the USA.
