Netherlands set an imposing target of 269 for victory and despite a great century by Craig Williams, Namibia were always playing catch up and finished well short of the target at the end.
Namibia elected to field after winning the toss and got off to a great start as Louis Klazinga struck with two great deliveries within the first five overs.
He clean bowled Stephan Myburgh for 4 and then clean bowled Michael Swart for 9 to leave Holland stuttering at two for 17.
Wesley Barresi and Tom Cooper however rebuilt Netherlands' innings with a 97-run third wicket partnership, before spinner LP van der Westhuizen bowled Cooper for 39, while Barresi was caught by Christi Viljoen off Bernard Scholtz' bowling for 60.
Daan van Bunge (28) and Tom de Grooth (44) added 58 for the fifth wicket while there were fine contributions at the end by Timm van der Gugten (23) and Mudassar Barresi (27 not out off 22 balls) as they reached 268 for 9 off 50 overs.
Klazinga was Namibia's best bowler, taking 3/48 off 10 overs, while LP van der Westhuizen took 2/49 off 10 overs.
Namibia's innings got off to a poor start as Raymond van Schoor was run out for a duck in the first over after a direct hit by Daan van Bunge.
Netherlands turned up the pressure with the dismissals of Xander Pitchers (12) and Pikky Ya France (6) in successive overs, as Namibia crashed to three wickets for 20 runs.
Craig Williams joined Stephan Baard and put Namibia's run chase back on track with a great innings, as he kept the scoreboard ticking with quick singles and some classic cover drives.
He reached his 50 off 62 balls and put on 94 for the third wicket before Baard was out caught on the boundary for 28.
Williams went on to reach his century before he was dismissed for 116 which came off 121 balls and included five fours and two sixes.
But he received little support as Sarel Burger was run out for 12 while LP van der Westhuizen was out for only one, caught off a top edge.
Nicolaas Scholtz added 37 off 38 balls, including two big sixes, but it was too little too late as the whole side was out for 237 with seven ball remaining.
Netherlands' best bowlers was Timm van der Gugten, who took three wickets for 37 runs.
The second ICC World Cricket League Championship match between the two sides takes place at the Wanderers field on Thursday.