The back-to-back wooden spooners were made to endure some Clint Gutherson brilliance, an onslaught of Eels attack in the first half and an unfortunate sin-binning of their most important player on the day, rookie five-eighth Lachie Galvin.
But a Morgan Harper knock-on in the final three minutes put Wests in position for a game-winning shot after they had trailed 14-6 with 17 minutes to play on Easter Monday.
Veteran halfback Sezer made no mistake with a flat drop goal that flew over the black dot.
The Eels had their own chance to snatch the game when the Tigers were called off-side from the restart.
But Gutherson's last-minute attempt at goal from the resultant penalty - from 37 metres out near the touchline - swung left of the upright, allowing the Tigers to hold on and score their first consecutive wins since last May.
"It's probably the most resilient performance we've had in a Tigers jersey for a long time," Marshall said.
"We don't care about what happened last year or the year before. We're on the 'now train'.
"Moving forward, we need to be better than we were today for where we want to go. There's still a lot of improvement in us."
Justin Olam has scored three tries in two games since joining the Tigers. (Mark Evans/AAP PHOTOS)
Eels coach Brad Arthur accused his side of chasing a "soft win" against the long-time easybeats, who now sit in sixth place with a 2-1 record under rookie coach Marshall.
"The last couple of weeks we've built our game about being tough and rolling the sleeves up," Arthur said.
"I don't know if we wanted to do that as much as they wanted to today."
All 28,608 pairs of eyes at CommBank Stadium were on the battle of young halves, with Galvin pitted against former high school classmate and Mitch Moses' injury replacement Blaize Talagi.
Galvin, who is set to face a two-match ban over his hip-drop tackle, drew first blood.
The 18-year-old threaded a grubber kick through the line that allowed Justin Olam to crash over for his first of two tries, and third in two games at his new club.
Galvin saved his best trick for last, giving the Tigers a 16-14 lead when he burst through Talagi on the left edge and found a flying Jahream Bula, who scored under the posts.
Gutherson had been the Eels' most important player, showing his class early by hooking a basketball-style pass over to Maika Sivo.
The hulking winger scored in his first game since receiving a three-match ban in the pre-season.
It was to be the Eels' only try of a gritty first half, with the Tigers repelling their hosts on the goal-line in six consecutive sets just before half-time.
Lachie Galvin was busy all day and instrumental in the Tigers' upset win. (Mark Evans/AAP PHOTOS)
Gutherson ran in support to help turn J'Maine Hopgood's burst of speed into Parramatta's first lead of the day just after the break.
The Eels appeared primed to go on with things after Galvin went to the sin bin for a hip-drop tackle on Kelma Tuilagi, which was only pulled up during a captain's challenge for an unrelated error.
Galvin has since been offered a two-game ban for the shot.
Gutherson gave Parramatta a chance with a penalty goal that tied the scores in the final six minutes, but veteran halfback Sezer slotted his 11th career field goal to confirm a famous victory.
