The 1976–77 Southern Football League season saw Wimbledon win the Premier Division. The club were elected to the Football League, replacing Workington.
Chelmsford City, Margate and Burton Albion were relegated from the Premier Division, whilst Worcester City, Barnet, Cheltenham Town and Hastings United were all promoted to the Premier Division, the former two as champions. Metropolitan Police left the league to join the Isthmian League.
The Premier Division featured four new clubs:
At the end of the season, the bottom four of the Football League had to be re-elected to retain their place. Whilst in previous seasons the number of non-League applicants had been unlimited, this season saw the Football League Management Committee limit the number to two, with Wimbledon and Northern Premier League members Altrincham (who had finished tenth) entering the ballot. The top four in the vote would retain/win a place in the League.
With 27 votes, Wimbledon finished fourth in the election, earning a place in the League at the expense of Workington, who dropped into the Northern Premier League.
Division One North featured three new clubs, all of which had been relegated from the Premier Division the previous season:
Division One South featured three new clubs