1983–84 Isthmian League

Premier Division

The Premier Division consisted of 22 clubs, including 20 clubs from the previous season and two new clubs, promoted from the First Division:

Also, at the end of the previous season Leytonstone & Ilford changed name into Leytonstone/Ilford.

Staines Town were demoted to the First Division due to ground grading, thus, Tooting & Mitcham United were reprieved.

League table

Source:
^† Wokingham Town were deducted three points.
Rules for classification: 1) points; 2) goal difference; 3) number of goals scored
(C) = Champion; (R) = Relegated; (P) = Promoted; (E) = Eliminated; (O) = Play-off winner; (A) = Advances to a further round.
Only applicable when the season is not finished:
(Q) = Qualified to the phase of tournament indicated; (TQ) = Qualified to tournament, but not yet to the particular phase indicated; (RQ) = Qualified to the relegation tournament indicated; (DQ) = Disqualified from tournament.

First Division

The First Division consisted of 22 clubs, including 18 clubs from the previous season and four new clubs:

Two clubs relegated from the Premier Division:

Two clubs promoted from the Second Division:

League table

Source:
Rules for classification: 1) points; 2) goal difference; 3) number of goals scored
(C) = Champion; (R) = Relegated; (P) = Promoted; (E) = Eliminated; (O) = Play-off winner; (A) = Advances to a further round.
Only applicable when the season is not finished:
(Q) = Qualified to the phase of tournament indicated; (TQ) = Qualified to tournament, but not yet to the particular phase indicated; (RQ) = Qualified to the relegation tournament indicated; (DQ) = Disqualified from tournament.

Second Division

Second Division consisted of 22 clubs, including 19 clubs from the previous season and three new teams:

Before the start of the season Dorking Town was renamed Dorking.

At the end of the season Corinthian Casuals resigned from the league, while the Second Division was split into Second Division North and Second Division South with a number of Athenian League clubs joining.

League table

Source:
^† Southall were deducted three points.
^* Horsham were deducted one point.
Rules for classification: 1) points; 2) goal difference; 3) number of goals scored
(C) = Champion; (R) = Relegated; (P) = Promoted; (E) = Eliminated; (O) = Play-off winner; (A) = Advances to a further round.
Only applicable when the season is not finished:
(Q) = Qualified to the phase of tournament indicated; (TQ) = Qualified to tournament, but not yet to the particular phase indicated; (RQ) = Qualified to the relegation tournament indicated; (DQ) = Disqualified from tournament.