[5] Parramatta saw very little success in their early years, despite narrowly missing out on finals qualification in 1949 under the guidance of former Western Suburbs and Leeds five-eighth Vic Hey.

Under the influence of coach Jack Gibson and with a team including names such as Ray Price, Peter Sterling, Eric Grothe, Sr., Steve Ella, Mick Cronin, and Brett Kenny the club captured three consecutive premierships from 1981 to 1983, beating the Newtown Jets in 1981 and the Manly-Warringah Sea Eagles in 1982 and 1983.

[19][20] The Eels reached the 2001 NRL Grand final after a dominant regular season, where they scored a total of 839 points and lost only 4 matches, but were defeated by the Newcastle Knights 30–24.

After 18 rounds and incredibly inconsistent form, the Parramatta Eels had won only 5 games and were sitting third-last and were in direct contention for the dreaded 2009 NRL Wooden Spoon.

Though beginning in Round 19, upset victories against the Melbourne Storm and the Canterbury-Bankstown Bulldogs set the platform for an unexpected 10 wins from the next 11 games, which propelled the Eels into the Top 8 and consequently, premiership contention.

This unanticipated winning streak was directly attributed by many sporting experts including Rugby League legend Andrew Johns to the spectacular run of form of star fullback Jarryd Hayne.

Winning the award for man-of-the-match in every game from Round 19–24, and again in the first week of the finals, Hayne was described as "the best player in any code of football in Australia" by premiership-winning coach Phil Gould.

The 2011 season was to be considered a year of "almosts" for Parramatta, with the team losing over half of their matches by four points or fewer, many of which were conceded after attaining leads over their opponents.

Parramatta pushed a record four games into Golden Point during the season, however were unable to win any, resulting in a draw against the St. George Illawarra Dragons and one-point losses to the Penrith Panthers, Sydney Roosters and the Canterbury-Bankstown Bulldogs.

Other switches include the moving of Luke Burt to fullback, second-rower Ben Smith to right centre, and the resting of five-eighth Daniel Mortimer.

Parramatta struggled all year, securing just their first win of the season in Round 5 against defending premiers Manly-Warringah Sea Eagles before ending a six-game losing streak against the Cronulla-Sutherland Sharks.

The team responded to this producing 3 wins from 4 games, including competition front-runners Melbourne Storm and Brisbane Broncos to give the fans some hope for the rest of the season.

Whilst Parramatta's problems in 2012 were largely attributed to their relatively poor defence, numerous pundits blamed them on the recurring absences of star fullback Jarryd Hayne.

Throughout the season many of the Parramatta players came under scrutiny and were dropped to the NSW Cup, including high-profile recruit Chris Sandow, who at the time was touted as overweight and unfit,[28] and veteran Luke Burt.

In round 24 Parramatta were sitting 8th on the ladder and looked destined to play in the finals for the first time since 2009 and only needed to win one of their last two remaining games against sides lower than them on the table which were Canberra and Newcastle.

[40] On 9 July, after over 2 months of club officials contesting the preliminary penalties, Parramatta were handed their punishment with the addition of their for/against points tally accumulated from rounds 1-9 being deducted.

[43][44][45] The 2016 season was also difficult for Parramatta as to become salary cap compliant the club needed to release players such as Nathan Peats and Junior Paulo to be able to play for points.

Star recruit Kieran Foran who signed only months earlier on a $1 million a year contract also walked out on the club mid-season due to numerous personal problems and off field issues.

In Round 6 of the 2019 NRL season, Parramatta played their first game at the new Western Sydney Stadium against the Wests Tigers and ran out 51–6 winners in front of a sold-out crowd.

[65][66] By round 18, the club sat entrenched within the top four of the competition with a six-point gap ahead of the fifth and sixth placed Sydney Roosters and Manly-Warringah.

Although they defeated Penrith and Melbourne twice, the club only managed to win more than three games consecutively on two separate occasions and lost to eventual wooden spooners the Wests Tigers in round 6 of the competition.

[74] In round 19, Parramatta suffered their biggest loss of the year losing 46–10 against the New Zealand Warriors with a number of key players missing due to injury and State of Origin selection.

Following the clubs round 3 victory over Manly, Parramatta were dealt a huge blow with halfback Mitchell Moses suffering a foot injury which ruled him on indefinitely.

[78][79][80] Following the clubs 48-16 loss against Melbourne at Magic Round, head coach Brad Arthur was terminated by Parramatta ending his ten-year tenure in charge.

[82] In round 12 of the 2024 NRL season, Parramatta suffered one of their most embarrassing losses in recent times losing 42-26 against South Sydney who were bottom of the table and only had one win to their name prior to the match.

Rugby league was played at Cumberland Oval from as early as 1909 by local clubs such as Parramatta Iona, Endeavours and the Western Districts representative side.

The largest ever rugby league attendance at Parramatta Stadium was set on 6 July 1994 when 27,918 saw Australia defeat France 58–0 in a one-off mid-season Test match.

[98] In round 21 of the 2022 NRL season, the two sides met at Brookvale Oval where Manly needed to defeat Parramatta if they were to stand any chance of reaching the finals.

Such players who have been at both clubs since 2000 include Jamie Lyon, Daniel Heckenberg, Shayne Dunley, Kylie Leuluai, Michael Witt, Aaron Cannings, Jack Afamasaga, Feleti Mateo, Richard Faʻaoso, Blake Green, Joe Galuvao, Tony Williams, Jeff Robson, Jonathan Wright, Justin Horo, Chris Hicks, Cheyse Blair, Darcy Lussick, Kelepi Tanginoa, Brayden Wiliame, Daniel Harrison, William Hopoate, David Gower, Anthony Watmough, Clinton Gutherson, Kieran Foran, Siosaia Vave, Shaun Lane, Andrew Davey, Joey Lussick, Michael Oldfield, Morgan Harper and Kelma Tuilagi.

Parramatta lead the match 16–8 with less than seven minutes to play but Penrith levelled the game at 16-16 after Nathan Cleary kicked a 40-metre field goal with seconds remaining.