Former Fulham and Tottenham star Dempsey netted a hat-trick and ex-Inter Milan and Newcastle United striker Martins had two assists as the Sounders produced a late show to deny the home side maximum points.
After the match, Dempsey spoke highly of the burgeoning partnership while Martins also touched on the dangerous aspect of the Sounders attack.
"Talking to Oba, we know we have to play well in order for this team to do well," Dempsey told reporters after the match.
"It's important to combine well and get that partnership, that relationship, that understanding of where each other is on the field. That's building."
Martins added: "It's what we do even in training.
"We love playing each other, trying to connect, trying to play well because that's the chance we have up front.
"This is just the beginning. I hope we'll play well and play a lot of games together."
Kenny Cooper (against his former club) gave Seattle the lead in just the third minute when he was on hand to slot home Jalil Anibaba's goal-bound effort from Gonzalo Pineda's corner six minutes before Diego Chara levelled when he struck from outside the area for his first goal in two-and-a-half years.
Diego Valeri then had the Timbers ahead in the 14th minute when he turned and rifled in under Stefan Frei's crossbar prior to Dempsey equalizing ten minutes later when receiving a slipped through ball from Martins to neatly finish beyond Andrew Weber.
Chara grabbed a second in the 55th minute with another long range strike and Maximiliano Urruti made it 4-2 just before the hour-mark with a curling effort but Dempsey had his say by scoring in the 85th minute before forcing a draw with a penalty moments later after DeAndre Yedlin had been felled in the area.
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