Wawrinka posted the first break of the match to win the first set and then won the first four games of the second before Gimeno-Traver rallied and forced the tiebreaker. Wawrinka was able to move ahead midway through the tiebreaker and closed things out from there.
Wawrinka's win led a four-match sweep by seeded players Wednesday.
No 4-seeded Juan Monaco had the clearest result, beating Guillermo Garcia-Lopez 6-1, 6-2 without facing a break point. Monaco won half of the points when receiving serve and nearly three-quarters off his serve.
Fifth-seeded Feliciano Lopez took out Andrey Kuznetsov 6-4, 6-3, firing off nine aces and saving the only break point he faced.
Wawrinka will go against Lopez and Monaco takes on Youzhny in Friday's quarterfinals.
Swim Week Miami Beach 2014 [PHOTOS]