Opener George Munsey hit 67 while Matthew Cross added 57 as the Scots posted 203 for seven.
Craig Williams led the charge with 80 for Namibia, who had beaten Scotland by five wickets four days ago.
Spinner Mark Watt got the key wicket of Williams, his second of the day, while Brad Wheal also took a couple of wickets in a high-scoring contest.Scotland open their World Cup campaign against Bangladesh on Sunday in Muscat while they will also face Oman and Papua New Guinea in Group ‘B’.
Namibia are in Group ‘A’, along with Sri Lanka, Ireland and the Netherlands.
Four teams will progress from the first round to join the Super 12 phase of the tournament.
Scotland: 203/7 in 20 overs (Munsey 67, Cross 57, Wiese 2/23)
Namibia: 184/ in 20 overs (Williams 80, Watt 2/34, Wheal 2/36). (BBC)