The win snaps a four-game losing streak for Port and compounds the disappointment for Essendon fans who have not seen their side win since the opening round of the season and have now endured two winless months.
The Power opened an early lead, but the Bombers were able to stay within striking distance for most of the first-half before Port skipped away with the result in the second.
It was a dirty night for the Dons who struggled to find a clear winner, but Nathan Lovett-Murray (21 possessions) and Mark McVeigh (25 touches) tried hard all night and were not disgraced.
Brendon Lade picked up 20 possessions, 25 hitouts and a goal - while his ruck partner Dean Brogan (19 disposals) was also good in his first game back after a month out with broken ribs.
Kane Cornes was his usual prolific self with 33 touches, while Danyle Pearce really caught the eye around the ball with 29 disposals.
Lade was instrumental in getting Port off to a good start, kicking his side's first goal and giving his midfield excellent service with some deft tapwork.
Brent Stanton got the scoreboard moving for Essendon, but the Power was getting the better of the midfield exchanges - Pearce busy with 10 disposals - and banged through four unanswered goals to bounce out to a 28-point lead.
The Bombers were under siege, but worked into the contest well and actually finished off the term better than the visitors in general play. A nice piece of work by Kepler Bradley ended a string of spurned chances, but Damon White got one against the run of play in the last minute of the quarter to see Port up by 19 points.
Both sides struggled to find the goals as the second quarter progressed, but a trademark Scott Lucas long bomb broke the sequence of misses 13 minutes in. The Dons continued to press, but were unable to exert any scoreboard pressure on the Power who went further ahead with goals to Nathan Lonie and Toby Thurstans.
The 26-point deficit at half-time was not insurmountable for the Bombers and it quickly got slimmer when Lucas banged through a vintage effort within a minute of the restart for his third.
Warren Tredrea still doesn't look 100 per cent and had little influence from full-forward in the first half, but he burst onto the scene in the third with three goals helping Port Adelaide break the game wide open.
Brogan took the ball out of the ruck to snap a beauty after Brett Ebert had taken a big grab in the goal-square and converted. Adam McPhee tried in vain to stem the flow with a fine effort from 50, but Port had a head of steam up now and slotted the last three goals of the term to open up an imposing 47-point lead at the last change.
The Bombers rallied with goals to Mark Bolton and McVeigh early in the last, but it was too little, too late as the Power closed out the match with the last three goals.
Despite keeping pace with Port in the first half, Sheedy felt the Bombers were never a serious threat to come away with a win.
"They just looked like they were pretty flat right from the start even though we perhaps matched Port Power for some of the game early … but at no stage did we ever really look like we were going to catch them," he said.
"We were really disappointing in our efforts today - there's no doubt about that - we actually were very disappointed."
ESSENDON: 3.6, 4.9, 7.10, 9.15 (69)
PORT ADELAIDE: 7.1, 9.5, 15.9, 20.9 (129)
GOALS – Essendon: Lucas 3, Stanton, Bradley, Watson, McPhee, McVeigh, Bolton
Port Adelaide: Tredrea 4, White 3, Ebert 2, Dew 2, Lade, S. Burgoyne, Wilson, Thomson, Lonie, Thurstans, Brogan, Pearce, Chaplin
BEST – Essendon: McVeigh, Lovett-Murray, Watson, Welsh, Lucas
Port Adelaide: Lade, Salopek, S. Burgoyne, Pearce, K. Cornes, Symes, Brogan, Lonie, Wakelin
INJURIES – Essendon: Nil
Port Adelaide: Nil
CHANGES – Essendon: nil
Port Adelaide: Nil
REPORTS - Nil
UMPIRES - Allen, Jeffery, Pannell
CROWD - 29,232 at Telstra Dome
