Namibia scored 236 for five wickets off their 50 overs, a total that was once again not enough as Holland reached 240 for nine with 12 balls remaining.
The result means that Netherlands have entrenched their second position on the log behind Ireland and stand a good chance of qualifying directly for the 2015 Cricket World Cup.
Namibia however remain second last on the log and are out of the running for direct qualification.
Namibia got off to a fine start after being put in to bat by the Netherlands as Raymond van Schoor and Xander Pitchers put on a century first wicket partnership.
Pitchers (48) and Stephan Baard were however both run out in quick succession as Namibia tried to up the run rate, while Craig Williams (9), Sarel Burger (7) and LP van der Westhuizen (1) were dismissed in quick succession
Nicolaas Scholtz however joined Van Schoor to put Namibia back on track with an unbroken 85-run partnership, with Van Schoor unbeaten on 93 and Scholtz unbeaten on 51 off 45 balls.
Peter Borren was Netherlands' best bowler with two wickets for 34 runs off eight overs.
Netherlands attacked from the outset as Michael Swart scored 16 off 14 balls before being bowled by Christi Viljoen, while Stephan Myburgh and Wesley Barresi shared a second wicket stand of 83 runs at nearly eight an over.
Williams once again got the breakthrough, bowling Barresi for 58 and Myburgh for 32 in quick succession to bring Namibia back into the game.
Williams also dismissed dangerman Tom Cooper for 15, and when Netherlands lost their next three wickets in quick succession, Namibia were back on top.
Bernard Scholtz bowled Peter Borren for eight, Tom de Grooth was dismissed by Louis Klazinga for one and Michael Rippon was run out for two.
But with a modest run rate required, Netherlands held their nerve, as Daan van Bunge took them to victory. He went on to score 60 before being caught with the score tied, while their last batsman Ahsan Malik hit the winning runs.
Namibia's best bowlers were Christi Viljoen with three wickets for 43 runs and Craig Williams with three for 58 runs.