Scrumhalf Kahn Fotuali'i and fullback Paul Williams also scored a try apiece, while referee Romain Poite awarded the Pacific islanders a penalty try for repeated scrum infringements by the Namibians close to their line.
Flyhalf Tusi Pisi slotted two conversions and a penalty before he went off in the 28th minute with a hamstring injury, while Williams, sinbinned in the first half for a shoulder charge on Namibia flyhalf Theuns Kotze, kicked a penalty and added three conversions.
Centre Danie van Wyk and Kotze scored consolation tries for the African side, while the flyhalf converted his effort under the posts.
Result: Samoa 49 (Alesana Tuilagi 3, Kahn Fotuali'i, , Paul Williams tries, penalty try; Tusi Pisi 2 con, 2 pen; Williams 3 con, pen), Namibia 12 (Danie van Wyk, Theuns Kotze tries; Kotze con).