The Eaton Recreation Centre was at capacity, with the Slammers making the finals for the first time since 2001.
However, East Perth quickly silenced the crowd with a display of outshooting as they quickly jumped out to a 10-point lead.
The lead was extended to 18 points at one stage in the second quarter, before the Slammers clawed it back to 50-37 at halftime.
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READ NOWJoe Alan Tupaea led all scorers at the half with 13 points at six from seven field goal shooting.
The second half was much of the same with the Eagles firing from three-point range. East Perth made 15 three pointers from 31 attempts and the game broke out to 36 points by the start of the fourth quarter.
Top performers for the game were Tupaea with 21 points, eight assists and eight rebounds while Mike Jones had 20 point with 60 per cent accuracy from three-point range.
Drew Williamson finished with 18 points and seven assists, while John Taylor came off the bench with 15 points of his own. Tom Jervis scored 14 points.
East Perth will be looking to wrap up the series and win game two on Friday night at Morley Recreation with an 8.30pm tip off.
If a deciding Game 3 is required, it will be played in Morley on Saturday.