It wasn't their most complete performance of the season, taking more than three quarters to shake the Bombers, who took a one-point lead into half-time and were still in the game early in the final term.
But, led by superb young midfielder Luke Shuey, the Eagles kicked the last seven goals of the game to notch their fifth straight win and their 10th in 11 games.
Shuey had 12 of his 23 possessions in a highly influential second half and he finished with a game-high 11 clearances - matched with NAB AFL Rising Star rival Dyson Heppell - who was also impressive for Essendon.
West Coast midfielders Daniel Kerr (25 possessions and two goals), Matt Priddis (27 and 10 clearances) and Scott Selwood (23 and eight tackles) were also important, while key forward Josh Kennedy got better each quarter, kicking 4.3.
The win could come at a cost, however, with vice-captain Beau Waters reported for rough conduct after collecting Essendon midfielder Jobe Watson high with a shoulder late in the third term.
Without their captain and leading clearance player, the Bombers struggled to win effective clearances in the centre, with West Coast winning the hit-outs 55-37.
They were also left stretched at both ends of the ground, with key position players Michael Hurley and Tayte Pears both left out of the travelling party with general soreness.
Patrick Ryder became the visitors' focal point in attack, kicking three goals, and Jake Carlisle was given the task of containing Kennedy, performing well in the first half.
But the 19-year-old, like his injury-hit team, fell away late in the game as the Eagles notched their eighth consecutive win over the Bombers in Perth.
The Bombers host struggling Port Adelaide at Etihad Stadium next Sunday before their round 24 bye.
West Coast 4.3 6.6 12.12 20.14 (134)
Essendon 3.0 7.1 9.5 11.11 (77)
GOALS
West Coast: Kennedy 4, LeCras 4, Kerr 2, Cox 2, Embley 2, Lynch 2, S. Selwood, Shuey, Nicoski, Naitanui
Essendon: Ryder 3, Crameri 2, Watson, Zaharakis, McVeigh, Jetta, Hocking, Lovett-Murray
BEST
West Coast: Shuey, Kerr, S. Selwood, Kennedy, Priddis, Embley, Cox
Essendon: Stanton, Heppell, Watson, Hocking, Ryder, Crameri
INJURIES
West Coast: Jack Darling replaced in selected side by Chris Masten
Essendon: Andrew Welsh (head), Stewart Crameri (shoulder)
SUBSTITUTES
West Coast: Ashton Hams replaced by Chris Masten in the third quarter
Essendon: Andrew Welsh replaced by Nathan Lovett-Murray in the first quarter
Reports: Beau Waters (West Coast) reported for rough conduct on Jobe Watson (Essendon) in the third quarter.
Umpires: Margetts, McInerney, Mollison
Official crowd:38,253 at Patersons Stadium