He played most of his club career for Blackburn Rovers, whose early embracing of professionalism enabled them to become one of the major teams in English football, and with whom he appeared on the winning side in five FA Cup finals.

Forrest was called up for his first England cap for their final match in the inaugural British Home Championship against Wales on 17 March 1884, still aged only 19, replacing Notts County's Stuart Macrae at left half.

Rovers had little difficulty getting past the Old Boys 5–1 to set up a repeat of the previous year's final against Queen's Park, who had come through replayed matches against Notts County and Nottingham Forest in their last two rounds.

A week before the semi-final, Forrest was selected for the Home Championship match against Ireland, together with his Rovers teammates, Herby Arthur, Joe Lofthouse and Jimmy Brown.

This time there was little controversy and it was soon clear that Rovers were the superior side,[12] even though Queen's Park fielded six players who had appeared in the England versus Scotland match two weeks earlier.

After 14 minutes, Forrest got the better of his marker Charles Campbell and was able to fire Rovers in front from close range, after Jimmy Brown's shot had come back off the goal-posts.

Although Walter Arnott did put the ball in the net just before half-time, referee Francis Marindin disallowed the "goal" for handball.

The Scots continued to attack, but Rovers increased their lead on 58 minutes when Brown, "who had played throughout like a man inspired",[12] added a second goal.

After the final whistle, the Scottish team were a little unhappy that Rovers had fielded players, including Forrest, whose amateur status was questionable – despite this, there was little doubt that professionalism was here to stay.

A 3–1 victory took Rovers through to a semi-final against the last surviving totally amateur side, Swifts who included England internationals Charlie and Arthur Bambridge, and George Brann.

Despite this, Swifts presented no more of a challenge than Rovers' earlier opponents and after a 2–1 victory in the semi-final, played at the County Cricket Ground, Derby on 13 March 1886, they were through to the final, where they were to meet West Bromwich Albion.

The replay took place at Derbyshire County Cricket Club's Racecourse Ground in Derby, the first time an FA cup final had been played outside London.

Blackburn Rovers started their campaign to claim the FA cup for a record fourth time with a bye as their first round opponents Halliwell withdrew.

As a result of Rovers' relative lack of success, none of their players were selected to represent England in the 1888 British Home Championship, with Forrest losing his place to Wolverhampton Wanderers's Harry Allen.

[21] as Blackburn finished the first league season in fourth place, a long way behind the champions Preston North End, who were now by far the strongest club in England, justly earning them the title of "The Invincibles".

[22] In the FA cup, after a victory over Accrington and a "walkover" past Swifts, Blackburn defeated Aston Villa 8–1 in the third round (with four goals from Jack Southworth) before going out in the semi-final to Wolverhampton Wanderers after a replay.

Before the cup final, Forrest (together with Rovers teammates Billy Townley, Joe Lofthouse, John Barton and Nat Walton) was selected for the England match against Ireland on 15 March 1890.

[24] This was Forrest's final appearance for England, in an international career which spanned seven seasons in which he played eleven times, with six victories, three draws and two defeats, both against Scotland.

From the kick-off, the Rovers forwards had the Wednesday defence under pressure which led to Jack Dungworth handling the ball on the edge of his goal area in the sixth minute.

The second half continued with Rovers on top with Jack Southworth adding a fourth goal in the fiftieth minute before Albert Mumford was able to score for Wednesday.

According to Gibbons, "the Blackburn side had given one of the finest exhibitions of attacking football in an FA cup final, with England internationals Walton, Townley, Lofthouse and John Southworth at the peak of their form.

"[26] Forrest continued to play at the centre of Blackburn's defence for the 1890–91 season, forming a settled half-back line alongside fellow internationals Jack Barton and Geordie Dewar.

Although County pulled a goal back in the second half, Rovers were able to defend their lead and thus claimed the cup for the second consecutive year, the fifth time overall.

Footnote: One source described Jimmy Forrest as an industrious half-back, whose tough tackling was matched by an intelligent reading of the game that enabled him to anticipate danger and intercept the ball before the opposition could fully develop an attack.