In mid-February, they lost a Fourth Division game for the first time in more than four months, after which two consecutive wins in mid-March took them to the top of the table.

Although Gillingham slipped from first place, they remained in the top three, and a victory over Colchester United on 20 April ensured that the team would be promoted to the Third Division at the end of the season.

In their final game of the season on 1 May, first-placed Gillingham lost to second-placed Peterborough United, who overtook them to win the championship of the division.

The highest attendance recorded at the club's home ground, Priestfield Stadium, was 12,297 for a game against Peterborough United on 3 April 1974.

[4] In June, Damien Richardson became the first Gillingham player to represent his country in a senior international match, when he played for the Republic of Ireland in a friendly away to Norway.

[5][a] Gillingham prepared for the new season with four friendlies in August, against Luton Town and Sheffield Wednesday of the Second Division, Brighton & Hove Albion of the Third, and semi-professional team Sittingbourne.

[8] Due to injuries sustained in pre-season, Alan Wilks and Keith Lindsey, both regular starters in the previous season, were absent from the team; Gillingham lost the match 1–0.

[8] Coxhill made his first appearance in the starting line-up in a 1–1 draw away to Scunthorpe on 23 October and was a regular starter for the remainder of the season.

[27] At the end of January, Gillingham were still second in the table, now three points behind Colchester United albeit with the advantage of having played one fewer game.

[28] Gillingham began February with victories over Lincoln City and Hartlepool to take their unbeaten league run to 20 games,[20][29] but then lost 3–2 away to Bury,[30] their first defeat in the Fourth Division since the previous October.

[20][33] The team then won two consecutive games 1–0, Richardson scoring the winning goal in both matches,[20] after which they were top of the Fourth Division table.

Gillingham entered the 1973–74 Football League Cup at the first round stage and were paired with fellow Fourth Division team Colchester United.

Gillingham won the match at Priestfield 4–2 to progress to the second round, where they were drawn to play Carlisle United of the Second Division, again at home.

[46] FW = Forward, MF = Midfielder, GK = Goalkeeper, DF = Defender Two days after the final match of the season, Nelson resigned as the club's manager to take over at Charlton Athletic of the Third Division.

[47] The club moved quickly to replace him with Len Ashurst, manager of Hartlepool, who was introduced to supporters at a promotion celebration event at the Central Hall in Chatham on 6 May.

[48] In his first season in charge, Gillingham finished 10th in the Third Division,[49] but in October 1975 he unexpectedly resigned to take the manager's job at Sheffield Wednesday, sparking a two-year dispute between the two clubs over financial compensation.